bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ecosystem Consequences of Enhanced Solar Ultraviolet Radiation: Secondary Plant Metabolites as Mediators of Multiple Trophic Interactions in Terrestrial Plant Communities¶
Authors: Bassman John H. 
Published: July 2010

ABSTRACTThe potential role of ultraviolet‐B (UV‐B)‐induced secondary plant metabolites as mediators of multiple trophic responses in terrestrial ecosystems is considered through review of the major classes of secondary metabolites, the pathways for their biosynthesis, interactions with primary and secondary consumers and known UV effects on their induction. Gross effects of UV‐B radiation on plant growth and survival under realistic spectral balances in the field have been generally lacking, but subtle changes in carbon allocation and partitioning induced by UV‐B, in particular production of secondary metabolites, can affect ecosystem‐level processes. Secondary metabolites are important in plant‐herbivore interactions and may affect pathogens. They act as feeding or oviposition deterrents to generalists and nonadapted specialists, but adapted specialists are stimulated to feed by these same compounds, which they detoxify and often sequester for use against their predators. This provides a route for tritrophic effects of enhanced UV‐B radiation whereby herbivory may be increased while predation on the herbivore is simultaneously reduced. It is in this context that secondary metabolites may manifest their most important role. They can be the demonstrable mechanism establishing cause and effect at higher trophic levels because the consequences of their induction can be established at all trophic levels.
UV Radiation Effects on Plant Growth and Forage Quality in a Shortgrass Steppe Ecosystem¶
Authors: Milchunas Daniel G. , King Jennifer Y. , Mosier Arvin R. , Moore John C. , Morgan Jack A. , Quirk Meghan H. , Slusser James R. 
Published: July 2010

ABSTRACTLevels of UV were manipulated in a native shortgrass steppe using open‐sided structures with tops that either passed or blocked wavelengths shorter than ∼370 nm. Precipitation was controlled to create a drought or a very wet year. Subplots were either nondefoliated or defoliated to simulate grazing by livestock, which is the primary land use. Plant community productivity and forage quality were assessed in response to the two climate change variables (UV, precipitation) and grazing stress. Productivity and seasonal standing biomass of the dominant grass species were negatively affected by passing versus blocking UV, but only in the dry year. Another species was negatively affected by passing UV in the wet year, indicating the potential for future shifts in species composition. Forage quality for ruminants increased when UV was passed compared with blocked, as determined by in vitro digestible dry matter, depending on species and precipitation. Nitrogen concentrations and soluble and fiber components of vegetation also displayed some UV effects, but they were generally small and depended on species, season or amount of precipitation (or all). Grazing treatment had large positive effects on current‐year productivity only in the wet year and some small positive effects on quality in both wet and dry years. Interactions between UV and grazing treatment were not observed.
Interactive Effects of Ultraviolet‐B Radiation and Temperature on Cotton Physiology, Growth, Development and Hyperspectral Reflectance¶
Authors: Reddy K. Raja , Kakanl Vijaya Gopal , Zhao Dull , Kotl Sallaja , Gao Wel 
Published: July 2010

ABSTRACTCurrent conditions of 2–11 kJ m−2 day−1 of UV‐B radiation and temperatures of >30°C during flowering in cotton cultivated regions are projected to increase in the future. A controlled environment study was conducted in sunlit growth chambers to determent the effects of UV‐B radiation and temperature on physiology, growth, development and leaf hyperspectral reflectance of cotton. Plants were grown in the growth chambers at three day/night temperatures (24/16° C, 30/22° C and 36/28° C) and three levels of UV‐B radiation (0, 7 and 14 kJ m−2 day−1) at each temperature from emergence to 79 days under optimum nutrient and water conditions. Increases in main stem node number and the node of first fruiting branch and decrease in duration to first flower bud (square) and flower were recorded with increase in temperature. Main effects of temperature and UV‐B radiation were significant for net photosynthetic rates, stomatal conductance, total chlorophyll and carotenoid concentrations of uppermost, fully expanded leaves during squaring and flowering. A significant interaction between temperature and UV‐B radiation was detected for total biomass and its components. The UV‐B radiation of 7 kJ m−2 day−1 reduced boll yield by 68% and 97% at 30/22°C and 36/28° C, respectively, compared with yield at 0 kJ m−2 day−1 and 30/22° C. No bolls were produced in the three temperature treatments under 14 kJ m−2 day−1 UV‐B radiation. The first‐order interactions between temperature, UV‐B radiation and leaf age were significant for leaf reflectance. This study suggests a growth‐ and process‐related temperature dependence of sensitivity to UV‐B radiation.
The Complex of Apomyoglobin with the Fluorescent Dye Coumarin 153¶
Authors: Chowdhury P. K. , Halder M. , Sanders L. , Arnold R. A. , Liu Y. , Armstrong D. W. , Kundu S. , Hargrove M. S. , Song X. , Petrich J. W. 
Published: July 2010

ABSTRACTUnderstanding a protein's dielectric response requires both a theoretical model and a well‐defined experimental system. The former has already been proposed by Song (J. Chem. Phys. 116, 9359 [2002]). We suggest that the latter is provided by the complex of coumarin 153 (C153) with apomyoglobin (ApoMb). C153 has been exhaustively studied and has proven to be an excellent probe of the solvation dynamics of polar solvents. Myoglobin is one of the most thoroughly studied proteins. Myoglobins from a wide range of species have been subject to X‐ray structural analysis and site‐directed mutagenesis. Here, we demonstrate the existence of a robust C153‐apomyglobin system by means of molecular dynamics simulations, equilibrium binding studies using a Job's plot and capillary electrophoresis, circular dichroism and time‐resolved fluorescence. The reorganization energy of C153 bound to ApoMb is compared with that of C153 in bulk solvent using the method of Jordanides et al. (J. Phys. Chem. B 103, 7995 [1999]).
Evaluation of 15 Polymerases and Phosphorothioate Primer Modification for Detection of UV‐induced C:G to T:A Mutations by Allele‐specific PCR¶
Authors: Gale James M. , Tafoya Gregory B. 
Published: July 2010

ABSTRACTAllele‐specific polymerase chain reaction is based on polymerase extension from primers that contain a 3′end base that is complementary to a specific mutation and inhibition of extension with wild‐type DNA due to a 3′end mismatch.Taqpolymerase is commonly used for this assay, but because of the high rate of nucleotide extension from primer 3′base mismatches documented forTaqpolymerase, high sensitivity is difficult to achieve. To determine whether other polymerases might improve assay sensitivity, 15 polymerases were tested with mutation‐specific primers for two ultravioletinduced mutations in the human 5S ribosomal RNA genes. Of the 15 polymerases tested, six were capable of discriminating these mutations at levels equivalent to or better thanTaqpolymerase. All primers were phosphorothioate modified on the 3′end to block removal of the critical 3′mutation‐specific base by polymerases containing 3′→ 5′exonuclease “proofreading” activity. The effectiveness of phosphorothioate modification was measured in mock polymerase chain reaction reactions and a time course. All six enzymes containing this exonuclease activity showed some ability to digest phosphorothioate‐modified primers and could be divided into two groups, showing fast and slow digestion kinetics. Of the three enzymes that showed slow digestion kinetics, two also showed significantly slower digestion kinetics of unmodified primers.
Mitochondria‐derived Reactive Oxygen Species Mediate Blue Light‐induced Death of Retinal Pigment Epithelial Cells¶
Authors: King Ayala , Gottlieb Eyal , Brooks David G. , Murphy Michael P. , Dunaief Joshua L. 
Published: July 2010

ABSTRACTThroughout the lifetime of an individual, light is focused onto the retina. The resulting photooxidative stress can cause acute or chronic retinal damage. The pathogenesis of age‐related macular degeneration (AMD), the leading cause of legal blindness in the developed world, involves oxidative stress and death of the retinal pigment epithelium (RPE) followed by death of the overlying photoreceptors. Evidence suggests that damage due to exposure to light plays a role in AMD and other age‐related eye diseases. In this work a system for lightinduced damage and death of the RPE, based on the human ARPE‐19 cell line, was used. Induction of mitochondriaderived reactive oxygen species (ROS) is shown to play a critical role in the death of cells exposed to short‐wavelength blue light (425 ± 20 nm). ROS and cell death are blocked either by inhibiting the mitochondrial electron transport chain or by mitochondria‐specific antioxidants. These results show that mitochondria are an important source of toxic oxygen radicals in blue light‐exposed RPE cells and may indicate new approaches for treating AMD using mitochondria‐targeted antioxidants.
Structural Heterogeneity of Cryotrapped Intermediates in the Bacterial Blue Light Photoreceptor, Photoactive Yellow Protein¶
Authors: Anderson Spencer , Šrajer Vukica , Moffat Keith 
Published: July 2010

ABSTRACTWe investigate by X‐ray crystallographic techniques the cryotrapped states that accumulate on controlled illumination of the blue light photoreceptor, photoactive yellow protein (PYP), at 110 K in both the wild‐type species and its E46Q mutant. These states are related to those that occur during the chromophore isomerization process in the PYP photocycle at room temperature. The structures present in such states were determined at high resolution, 0.95–1.05Å. In both wild type and mutant PYP, the cryotrapped state is not composed of a single, quasitransition state structure but rather of a heterogeneous mixture of three species in addition to the ground state structure. We identify and refine these three photoactivated species under the assumption that the structural changes are limited to simple isomerization events of the chromophore that otherwise retains chemical bonding similar to that in the ground state. The refined chromophore models are essentially identical in the wild type and the E46Q mutant, which implies that the early stages of their photocycle mechanisms are the same.
Metronomic Photodynamic Therapy as a New Paradigm for Photodynamic Therapy: Rationale and Preclinical Evaluation of Technical Feasibility for Treating Malignant Brain Tumors¶
Authors: Bisland Stuart K. , Lilge Lothar , Lin Annie , Rusnov Robert , Wilson Brian C. 
Published: July 2010

ABSTRACTThe concept of metronomic photodynamic therapy (mPDT) is presented, in which both the photosensitizer and light are delivered continuously at low rates for extended periods of time to increase selective tumor cell kill through apoptosis. The focus of the present preclinical study is on mPDT treatment of malignant brain tumors, in which selectivity tumor cell killing versus damage to normal brain is critical. Previous studies have shown that low‐dose PDT using 5‐aminolevulinic acid (ALA)‐induced protoporphyrin IX(PpIX) can induce apoptosis in tumor cells without causing necrosis in either tumor or normal brain tissue or apoptosis in the latter. On the basis of the levels of apoptosis achieved and model calculations of brain tumor growth rates, metronomic delivery or multiple PDT treatments, such as hyperfractionation, are likely required to produce enough tumor cell kill to be an effective therapy. In vitro studies confirm that ALA‐mPDT induces a higher incidence of apoptotic (terminal deoxynucleotidyl transferase‐mediated 2′‐deoxyuridine 5′‐triphosphate, sodium salt nick‐end labeling positive) cells as compared with an acute, high‐dose regimen (ALA‐αPDT). In vivo, mPDT poses two substantial technical challenges: extended delivery of ALA and implantation of devices for extended light delivery while allowing unencumbered movement. In rat models, ALA administration via the drinking water has been accomplished at very high doses (up to 10 times therapeutic dose) for up to 10 days, and ex vivo spectro‐fluorimetry of tumor (9L gliosarcoma) and normal brain demonstrates a 3–4 fold increase in the tumor‐to‐brain ratio of PpIX concentration, without evidence of toxicity. After mPDT treatment, histological staining reveals extensive apoptosis within the tumor periphery and surrounding microinvading colonies that is not evident in normal brain or tumor before treatment. Prototype light sources and delivery devices were found to be practical, either using a laser diode or light‐emitting diode (LED) coupled to an implanted optical fiber in the rat model or a directly implanted LED using a rabbit model. The combined delivery of both drug and light during an extended period, without compromising survival of the animals, is demonstrated. Preliminary evidence of selective apoptosis of tumor under these conditions is presented.
A Multicomponent Model of Chromophoric Dissolved Organic Matter Photobleaching¶§
Authors: Goldstone Jared V. , Del Vecchio Rossana , Blough Nell V. , Voelker Bettina M. 
Published: July 2010

ABSTRACTLight absorption by chromophoric dissolved organic matter (CDOM) plays a number of roles in natural waters, including both control of the underwater light field and the initiation of many photochemical reactions. A multicomponent analysis was used to describe the effects of UV and visible radiation on the optical absorption spectra of two natural water samples, a Suwannee River fulvic acid standard (SRFA) and a Delaware Bay water sample. This analysis used a constrained minimization technique to fit independent spectral components to the observed bleaching behavior of the water samples under monochromatic irradiation. Spectra derived from these fits were used to predict the bleaching behavior of both samples under polychromatic irradiation (λ< 320 nm). This approach reproduces the kinetics and spectral behavior of polychromatic photobleaching very well at times <48 h, but underpredicts the bleaching at longer time periods.
Identification of Genes Responsive to UV‐A Radiation in Human Lens Epithelial Cells Using Complementary DNA Microarrays¶
Authors: Andley Usha P. , Patel Harendra C. , XI Jing‐Hua , Bai Fang 
Published: July 2010

ABSTRACTUV‐A radiation produces cataract in animals, enhances photoaging of the lens and skin and increases the phototoxicity of drugs. However, the nature of genes that are activated or repressed after cellular exposure to UV‐A radiation remains enigmatic. Because lens epithelial cells exposed to UV‐A radiation undergo apoptosis 4 h after exposure to the stress, we sought to establish the change in gene expression in cells by UV‐A radiation using gene expression profiling using complementary DNA microarrays containing about 12000 genes. We identified 78 genes abnormally expressed in UV‐A‐irradiated cells (showing > 2.5‐fold change at P < 0.05). These genes are implicated in various biological processes, including signal transduction and nucleic acid binding, and genes encoding enzymes. A majority of the genes were downregulated. Our analysis revealed that the expression of genes for the transcription factors ATF‐3 and Pilot increased four‐fold, whereas the gene for the apoptosis regulator NAPOR‐1 decreased five‐fold. These changes were confirmed by real‐time quantitative reverse transcriptase‐polymerase chain reaction. The calpain large polypeptide 3 (CANP3) gene also increased nine‐fold after UV‐A radiation. In addition, peroxisomal biogenesis factor 7, glucocorticoid receptor‐α and tumor‐associated calcium signal transducer genes decreased three‐ to eight‐fold. Western blot analysis further confirmed the increase in protein expression of ATF‐3 and CANP3 and decreased expression of glucocorticoid receptor‐α in the irradiated cells. Surprisingly, most of these genes had not been previously shown to be modulated by UV‐A radiation. Our results show that human lens epithelial cells respond to a single dose of UV‐A radiation by enhancing or suppressing functionally similar sets of genes, some of which have opposing functions, around the time at which apoptosis occurs. These studies support the intriguing concept that activation of competing pathways favoring either cell survival or death is a means to coordinate the response of cells to UV‐A stress.
Fluorescence Lifetime Spectroscopy of Glioblastoma Multiforme¶
Authors: Marcu Laura , Jo Javier A. , Butte Pramod V. , Yong William H. , Pikul Brian K. , Black Keith L. , Thompson Reid C. 
Published: July 2010

ABSTRACTFluorescence spectroscopy of the endogenous emission of brain tumors has been researched as a potentially important method for the intraoperative localization of brain tumor margins. We investigated the use of time‐resolved, laser‐induced fluorescence spectroscopy for demarcation of primary brain tumors by studying the time‐resolved spectra of gliomas. The fluorescence of human brain samples (glioblastoma multiforme, cortex and white matter: six patients, 23 sites) was induced ex vivo with a pulsed nitrogen laser (337 nm, 3 ns). The time‐resolved spectra were detected in a 360–550 nm wavelength range using a fast digitizer and gated detection. Parameters derived from both the spectral‐ (intensities from narrow spectral bands) and the time domain (average lifetime) measured at 390 and 460 nm were used for tissue characterization. We determined that high‐grade gliomas are characterized by fluorescence lifetimes that varied with the emission wavelength (>3 ns at 390 nm, <1 ns at 460 nm) and their emission is overall longer than that of normal brain tissue. Our study demonstrates that the use of fluorescence lifetime not only improves the specificity of fluorescence measurements but also allows a more robust evaluation of data collected from brain tissue. Combined information from both the spectraland the time domain can enhance the ability of fluorescencebased techniques to diagnose and detect brain tumor margins intraoperatively.
Laser Techniques in the Study of Drug Photochemistry¶
Authors: Cosa Gonzalo , Scalano J. C. 
Published: July 2010

ABSTRACTThis review describes the application of different laser time‐resolved techniques, such as time‐resolved fluorescence, phosphorescence and laser flash photolysis, to elucidate the mechanism of drug photodegradation. The assignment of transient species based on their luminescence or absorption spectra and based on their reactivity to various quenchers is illustrated. The mathematical expressions used in fitting measured transient decays over time are also discussed. Practical situations found in the literature and relevant to drug photodegradation illustrate different examples. The importance of laser power, concentration and absorbance of the ground state, as well as other parameters intrinsic to laser techniques are discussed.
Phtodeceomposition of Pigment Yellow 74, a Pigment Used in Tattoo Inks¶
Authors: Cul Yanyan , Spann Andrew P. , Couch Letha H. , Gopee Neera V. , Evans Frederick E. , Churchwell Maona I. , Williams Lee D. , Doerge Daniel R. , Howard Paul C. 
Published: July 2010

ABSTRACTTattooing has become a popular recreational practice among younger adults over the past decade. Although some of the pigments used in tattooing have been described, very little is known concerning the toxicology, phototoxicology or photochemistry of these pigments. Seven yellow tattoo inks were obtained from commercial sources and their pigments extracted, identified and quantitatively analyzed. The monoazo compound Pigment Yellow 74 (PY74; CI 11741) was found to be the major pigment in several of the tattoo inks. Solutions of commercial PY74 in tetrahydrofuran (THF) were deoxygenated using argon gas, and the photochemical reaction products were determined after exposure to simulated solar light generated by a filtered 6.5 kW xenon arc lamp. Spectrophotometric and high‐pressure liquid chromatography (HPLC) analyses indicated that PY74 photodecomposed to multiple products that were isolated using a combination of silica chromatography and reversed‐phase HPLC. Three of the major photodecomposition products were identified by nuclear magnetic resonance and mass spectrometry as N(2‐methoxyphenyl)‐3‐oxobutanamide (o‐acetoacetanisidide), 2‐(hydroxyimine)‐N‐(2‐methoxyphenyl)‐3‐oxobutanamide and N,N″‐bis(2‐methoxyphenyl)urea. These results demonstrate that PY74 is not photostable in THF and that photochemical lysis occurs at several sites in PY74 including the hydrazone and amide groups. The data also suggest that the use of PY74 in tattoo inks could potentially result in the formation of photolysis products, resulting in toxicity at the tattoo site after irradiation with sunlight or more intense light sources.
Molecular Mechanism(s) for UV‐B Irradiation‐Induced Glutathione Depletion in Cultured Human Keratinocytes¶
Authors: Zhu Ming , Bowden G. Tim 
Published: July 2010

ABSTRACTGlutathione (GSH) plays a centxral role in maintenance of cellular redox homeostasis and protection against oxidative injury. Ultraviolet B (UV‐B) irradiation‐induced GSH depletion is believed to be involved in the pathogenesis of several cutaneous disorders. In this study, the molecular mechanism(s) of UV‐B‐induced GSH depletion was investigated in cultured human keratinocytes, HaCaT cells. We found that UV‐B irradiation caused GSH depletion in a dose‐ and timedependent manner in HaCaT cells. The mechanistic studies showed that UV‐B‐induced GSH depletion did not result from the GSH efflux. UV‐B irradiation appeared to cause a slight decrease in enzymatic activity of y‐glutamate cysteine ligase (GCL), a rate‐limiting enzyme in GSH biosynthesis. UV‐B irradiation resulted in the GCL cleavage through the activation of a caspase cascade. Inhibition of total caspase activity by the general caspase inhibitor, zVAD‐fmk, partially reversed the UV‐B‐induced GSH depletion. More importantly, we found that UV‐B irradiation could dramatically decrease the cystine uptake through the functional inhibition of the system Xc−, a cystine transporter on the cell membrane. The results suggest that the inactivation of cystine transporter system Xc− was a major contributor to the UV‐B‐mediated decrease of GSH levels in human keratinocytes.