bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Skin Immune System in the Course of HIV‐1 Infection
Authors: Henry Michael , Tschachler Erwin 
Published: January 2008

AbstractIn human immunodeficiency virus‐1 (HIV‐1) infection, diseases of the skin and mucous membranes frequently dominate the clinical picture as a consequence of progressive immunodeficiency. Functional impairment of the skin immune system, manifesting as a loss of the skin delayed‐type hypersensitivity response is very likely due to the infection of immunocompetent cells of the skin by HIV‐1. Besides CD4+ T cells, antigen‐presenting Langerhans cells have been established as major targets of HIV‐1 infection. The close physical contact of Langerhans cells with T lymphocytes during immune activation suggests a central role of these cells in the dissemination of HIV‐1 and the subsequent breakdown of the skin immune system. In addition, there are indications that mucosal Langerhans cells may represent prefered target cells for certain HIV‐1 subtypes and thereby facilitate mucocutaneous transmission of HIV‐1.
Fluorescence Quenching of 1‐Pyrenemethanol by Methylviologen in Polystyrene Latex Dispersions
Authors: Nakashima Kenichi , Kido Naofumi 
Published: January 2008

AbstractFluorescence quenching of 1‐pyrenemethanol by methylviologen through photoinduced electron transfer is investigated in polystyrene (PS) latex dispersions as well as in aqueous homogeneous solutions. In aqueous homogeneous solutions, the Stern‐Volmer plot for the intensity is linear and close to that for the lifetime, indicating a dynamic quenching mechanism. In PS latex dispersions, however, the Stern‐Volmer plots for the intensity are downward curving and the decay curves are not so much affected by the quencher as those for aqueous solutions, implying a significant contribution of static quenching. The downward‐curving Stern‐Volmer plots are well described by a two‐site model that assumes accessible and inaccessible sites to the acceptor on latex particles. The Stern‐Volmer constants obtained indicate that in the latex dispersions the fluorescence quenching occurs several hundreds times more efficiently than that in an aqueous homogeneous solution. This drastic enhancement of the quenching in latex dispersions is attributed to the increase in the local concentrations of the reactants on the latex surface. We have demonstrated the usefulness of latex surfaces as a new type of reaction field for photoinduced electron transfer.
OpticalIy Pumped Chemiluminescence of Indole‐3‐Acetic Acid
Authors: Krylov Sergey N. , Krylova Svetlana M. 
Published: January 2008

ABSTRACTOptically pumped chemiluminescence of indole‐3‐acetic acid (IAA) was observed and studied. Rose Bengal (RB) was used as a photosensitizer. Long‐lived chemiluminescence (CL) appeared after irradiation of the IAA/RB reaction mixture by monochromatic light at 550 nm (the maximum of RB absorption) or by visible light. The CL spectrum had a maximum at 480 nm. The kinetics of the CL decay were single exponential. Single‐exponential kinetics were characterized by two experimentally measured values: initial CL intensity and exponential lifetime of the CL decay. We studied the influence of five parameters: (1) the rate of irradiation fluence, (2) the time of irradiation, (3) RIB concentration, (4) IAA concentration and (5) buffer pH on the initial CL intensity and the CL lifetime. Initial CL intensity was proportional to the rate of irradiation fluence and the concentration of RB. Saturation was observed in dependencies of initial CL intensity on the time of irradiation, the concentration of IAA and the buffer pH. The lifetime of the CL decay decreased with increasing pH and did not depend on the other four parameters. The mechanism explaining the experimental results was suggested and detailed kinetic analysis was performed to prove the proposed mechanism. Quantum yield of the CL and five rate constants that are involved in the mechanism were determined.
UVA II Exposure of Human Skin Results in Decreased Immunization Capacity, Increased Induction of Tolerance and a Unique Pattern of Epidermal Antigen‐Presenting Cell Alteration
Authors: LeVee Gordon J. , Oberhelman Lois , Anderson Tom , Koren Hillel , Cooper Kevin D. 
Published: January 2008

Abstract— The risks incurred from increased exposure to UVA II (320‐340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon arc lamp filtered with a narrow bandpass filter (335 ± 5 nm full width at half maximum), individuals were contact‐sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II‐exposed group, as compared to 3.8% in the controls (P= 0.006). UVA II also uniquely altered the type of antigen‐presenting cells present in the epidermis. Human leukocyte antigen (HLA)‐DR+ cells in control epidermal cell suspensions (C‐EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1ahi DRmid CD11b− CD36− (1.5 ± 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 ± 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a DRhi CD11b+ CD36+ were increased in UVA II skin, relative to C‐EC, these comprised only 10.1 ± 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II‐EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CDllb+; these comprised 11.1 ± 6.9% of the DR+ UVA II‐EC.In conclusion, despite the above differences in infiltrating DR cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.
New Entrance Optics for Solar Spectral UV Measurements
Authors: Bernhard Germar , Seckmeyer Gunther 
Published: January 2008

ABSTRACTThe investigation of the impact of solar UV radiation on the biosphere requires spectral measurements of solar UV radiation of high accuracy. However, the accuracy of current measurements is limited, and this can partly be attributed to the entrance optics of the instruments used for these examinations. The angular response of spectro‐radiometers measuring spectral global UV irradiance should be given by the cosine of the incidence angle. In‐tercomparison campaigns have shown that deviations from this ideal cosine response lead to uncertainties in solar measurements of more than 10%. Here we present recently developed entrance optics that reduce these uncertainties to ±4% in the UV. The new entrance optics have been characterized with respect to their angular response, transmission, weather durability, fluorescence and dependence of the angular response on wavelength and polarization. Solar spectroradiometric measurements carried out with the new optics were compared with simultaneously performed measurements of a second spectroradiometer that was equipped with a conventional diffuser. The deviations of up to 12% between both systems are quantitatively explained to within 3%.
Quinolone Antibiotic Photodynamic Production of 8‐Oxo‐7,8‐dihydro‐2‘‐deoxyguanosine in Cultured Liver Epithelial Cells
Authors: Rosen J. E. , Prahalad A. K. , Schluter G. , Chen D. , Williams G. M. 
Published: January 2008

ABSTRACTTo study the basis for the phototoxicity of quinolones, a class of synthetic antibacterials, the photodynamic ability to mediate 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐oxo‐dG) formation in cultured cells was measured for lome‐floxacin (LMX), which is strongly associated with clinical phototoxicity in humans, and ciprofloxacin (CFX), which has few reports of phototoxicity. Adult rat liver (ARL‐18) cells were exposed to the quinolones in the presence of UVA and DNA was extracted and analyzed by HPLC with electrochemical detection. Low levels of 8‐oxo‐dG were found in the DNA of nonirradiated ARL‐18 cells and this was increased up to 6‐fold in the presence of either LMX (50–400 uAf) or up to 3.6‐fold in the presence of CFX (50–400 µM) and UVA (20 J/cm2) when compared to the UVA control. Comparing separate experiments with LMX and CFX, LMX produced greater levels of 8‐oxo‐dG either after dark exposure or after UVA exposure at 20 J/cm2. Also, LMX and CFX were both shown to photodegrade in the presence of UVA, and it was determined that UVA photoinstability alone does not reflect phototoxic potential. These data suggest that the photodynamic potential of LMX and CFX to produce 8‐oxo‐dG may relate to their human clinical phototoxicity profile. We suggest that the observed clinical phototoxicity is mediated through a UVA photodynamic effect on the quinolone to form reactive oxygen species in the presence of molecular oxygen. The findings indicate that 8‐oxo‐dG formation can serve as a marker for the potential phototoxicity of new quinolones.
Charge Movements in the 13‐c/s Photocycles of the Bacteriorhodopsin Mutants R82K and R82Q*
Authors: Misra Saurav , Ebreyf Thomas G. , Crouch Rosalie K. , Menick Donald R. 
Published: January 2008

ABSTRACTWe have examined light‐induced currents in oriented membranes of the bacteriorhodopsin mutants R82K and R82Q. Our results suggest that two photocurrent components found in R82K, with 30 and 300 us lifetimes, are due to the photocycle of the 13‐cis rather than the all‐trans form of the pigment. We investigated the pH dependence of these components and their correspondence to absorbance changes at 660 nm characteristic of pho‐tointermediates of the 13‐cis cycle. The presence of a D2O effect suggests that the charge motions producing these photocurrents are related to proton or protonated amino acid movement within the molecule. The current amplitudes depend on the protonation states of at least two residues, D85 and (probably) E204. In R82Q, a 10 pis photocurrent is observed that also depends on the protonation state of D85 and is similar to the 30 us current in R82K. We attempt to explain these currents in terms of a model for interacting residues in the extracellular half of the bacteriorhodopsin channel.
Diamino Acid Derivatives of Porphyrins Penetrate into Yeast Cells, Induce Photodamage, but Have No Mutagenic Effect
Authors: Zofadek Teresa , Nhi Nguyen Bich , Jagietto Izabella , Graczyk Alfreda , Rytka Joanna 
Published: January 2008

AbstractThe yeast Saccharomyces cerevisiae was used as a model eukaryotic organism to study the uptake of diamino acid derivatives of porphyrins and their phototoxicity with particular emphasis on possible mutagenic effects. The water‐soluble hematoporphyrin derivatives diarginate (HpD[Arg]2) and 1‐arginin di(N‐amino acid)‐protoporphyrinate used in this study are effective photosensitizers in tumor photodynamic therapy. Depending on the amino acid substituent, the porphyrin derivatives differ in their affinity for yeast cells. It is shown that HpD(Arg)2 and PP(Met)2 (Arg)2 penetrate into the yeast cell and are metabolized. Both compounds sensitize yeast cells to photodamage but have no mutagenic effect on nuclear or mitochondrial genomes.
Sun Exposure, Sunscreen and Their Effects on Epidermal Langerhans Cells
Authors: Neale Rachel , Russell Anne , Muller H. Konrad , Green Adele 
Published: January 2008

Abstract This study examined the effects of chronic and current sun exposure on the number of Langerhans cells in epidermal sheets of UV‐exposed and unexposed skin of the arms and assessed the effect of sunscreens. Participants were enrolled in a skin cancer prevention trial and had been using sunscreen daily for the previous 3 years. There were significantly fewer Langerhans cells on the exposed (463 cells/mm2) than on the unexposed forearm (528 cells/mm2) (P = 0.0001). High sun exposure in the previous 2 weeks and a history of predominantly outdoor occupations were both associated with a reduced number of Langerhans cells, although age and other biological indicators of chronic exposure were not associated. Sunscreen use was protective against the effects of current but not chronic sun exposure, with a suggestion of a greater effect at higher levels of exposure. Unexpectedly, people with a past history of nonmelanoma skin cancer had more Langerhans cells in both the exposed and the unexposed skin. These results emphasize the need for continued public health education to protect the immune system from the damaging effects of UV radiation.
Increased Photosensitivity in HL60 Cells Expressing Wild‐Type p53
Authors: Fisher Anita M. R. , Danenberg Kathleen , Banerjee Debabrata , Bertino Joseph R. , Danenberg Peter , Gomer Charles J. 
Published: January 2008

Abstract Loss of p53 function has been correlated with decreased sensitivity to chemotherapy and radiation therapy in a variety of human tumors. Comparable analysis of p53 status with sensitivity to oxidative stress induced by pho‐todynamic therapy has not been reported. In the current study we examined photosensitivity in human promye‐locytic leukemia HL60 cells exhibiting either wild‐type p53, mutated p53 or deleted p53 expression. Experiments were performed using a purpurin, tin ethyl etiopurpurin (SnET2)‐, or a porphyrin, Photofrin (PH)‐based photo‐sensitizer. Total SnET2 accumulation was comparable in all three cell lines. Uptake of PH was highest in cells expressing wild‐type p53 but incubation conditions could be adjusted to achieve equivalent cellular PH levels during experiments that analyzed photosensitivity. Survival measurements demonstrated that HL60 cells expressing wild‐type p53 were more sensitive to PH‐ and SnET2‐mediated photosensitization, as well as to UVC irradiation, when compared to HL60 cells exhibiting deleted or mutated p53 phenotypes. A rapid apoptotic response was observed following purpurin‐ and porphyrin‐induced photosensitization in all cell lines. Results of this study indicate that photosensitivity is increased in HL60 cells expressing wild‐type p53 and that photosensitizer‐medi‐ated oxidative stress can induce apoptosis through a p53‐independent mechanism in HL60 cells.
PhotochemCAD‡: A Computer‐Aided Design and Research Tool in Photochemistry
Authors: Du Hai , Fuh Ru‐Chun Amy , Li Junzhong , Corkan L. Andrew , Lindsey Jonathan S. 
Published: January 2008

AbstractA database of absorption and fluorescence spectra, including molar absorption coefficients and fluorescence quantum yields, has been compiled for 125 photochemically relevant compounds. An accompanying program enables calculation of oscillator strengths, natural radiative lifetimes, transition dipole moments, Forster energy‐transfer rates, multicomponent analysis, simulations of fluorescence spectra upon energy transfer among linear arrays of pigments, calculations of blackbody radiator curves at different temperatures and Lorentzian and Gaussian peak distributions. The program runs under Windows 95 and is equipped with extensive literature references and help features.
The Origin of115–130°C Thermoluminescence Bands in Chlorophyll‐Containing Material
Authors: Vavilin Dmitrii V. , Ducruet Jean‐Marc 
Published: January 2008

AbstractHigh‐temperature thermoluminescence (TL) emitted in the temperature region from +50 to +150°C has been studied in a variety of chlorophyll‐containing samples that were allowed to dry during the TL measurement. Analysis of the recorded traces by a multicomponent‐fit‐ting procedure revealed the existence of up to three bands of nonphotosynthetic origin with peak positions at62–75,114–128 and151–157°C and apparent activation energies of 27.0‐28.8, 14.1‐15.4 and 22.1‐23.3 kcal/mol (the bands are denoted as HT1 HT2 and HT3, respectively). Low‐temperature treatment of leaves, incubation of algae in the presence of paraquat, exposure of algae or isolated thylakoids to a strong light, all conditions known to stimulate oxidative damage to membrane lipids, caused appearance of a small HT1, band and significant rise in the intensity of the HT2 band. The increase in the HT2 component correlated positively with accumulation of conjugated dienes and malondialdehyde in thylakoids illuminated with a strong light. Different quenchers of active oxygen species and scavengers of free radicals added to preilluminated thylakoids or thylakoid lipid extracts before the TL measurements, as well as injection of argon into the TL measuring chamber, caused no changes in the intensity of the HT2 emission. The HT2 band in the thylakoids increased strongly upon addition of linoleate peroxidized by hydroxyradicals generated in the Fenton reaction but remained unchanged if the linoleate was oxidized with the use of lipoxygenase. We suggest that the HT2 band arises due to thermal decomposition of lipid cyclic peroxides present in the samples. In turn, the decomposition reaction leads to formation of carbonyls in triplet state with following migration of excitation energy toward chlorophyll. Contrary to the HT1, and HT2 bands, the HT3 band of TL cannot be associated with the thermolysis of lipid peroxidation products already present in the samples before starting the TL gradient.
Skin Necrosis due to Photodynamic Action of Benzoporphyrin Depends on Circulating Rather than Tissue Drug Levels: Implications for Control of Photodynamic Therapy
Authors: Lin Gloria C. , Tsoukas Maria L. , Lee Margaret S. , González Salvador , Vibhagool Chitralada , Anderson R. Rox , Kollias Nikiforos 
Published: January 2008

AbstractIn an ideal world, photodynamic therapy (PDT) of abnormal tissue would reliably spare the surrounding normal tissue. Normal tissue responses set the limits for light and drug dosimetry. The threshold fluence for necrosis (TFN) was measured in normal skin following intravenous infusion with a photosensitizer, benzoporphyrin derivative monoacid ring A (BPD‐MA) Verteporfin as a function of drug dose (0.25‐2.0 mg/kg), wavelength of irradiation (458 and 690 nm) and time interval (0–5h) between drug administration and irradiation. The BPD‐MA levels were measured in plasma and skin tissue to elucidate the relationship between TFN, drug kinetics and biodistribution. The PDT response of normal skin was highly reproducible. The TFN for 458 and 690 nm wavelengths was nearly identical and the estimated quantum efficiency for skin response was equal at these two wavelengths. Skin phototoxicity, quantified in terms of 1/ TFN, closely correlated with the plasma pharmacokinetics rather than the tissue pharmacokinetics and was quadratically dependent on the plasma drug concentration regardless of the administered drug dose or time interval between drug and light exposure. This study strongly suggests that noninvasive measurements of the circulating drug level at the time of light treatment will be important for setting optimal light dosimetry for PDT with liposomal BPD‐MA, a vascular photosensitizer.
Characterization of the Transient Intermediates Generated from the Photoexcitation of Nabumetone: A Comparison with Naproxen
Authors: Martínez Lydia J. , Scaiano J. C. 
Published: January 2008

AbstractThe photochemical and photophysical properties of nabumetone (4‐[6‐methoxy‐2‐naphthyl]‐2‐butanone) were examined employing conventional and time‐resolved spectroscopic techniques. The naphthalene‐like nabumetone triplet is formed with 29% efficiency in acetonitrile. Singlet oxygen formation was also detected in this solvent with a φA value of 0.19. A naphthalene‐like radical cation absorption, formed via biphotonic processes, was also detected. The reactivity of both the triplet and radical cation of nabumetone toward different substrates was examined. The photochemical properties of nabumetone are compared with those of naproxen, a structurally related acidic nonsteroidal anti‐inflammatory drug. For these two anti‐inflammatory agents, a type II photosen‐sitization process is most likely responsible for their phototoxicity.
Structure and Medium‐Dependent Photodecomposition of Fluoroquinolone Antibiotics
Authors: Fasani Elisa , Profumo Antonella , Albini Angelo 
Published: January 2008

AbstractThe photochemical reactivity of four fluoroquinolone antibiotics is examined. For norfloxacin (NOR), enoxacin (ENX) and lomefloxacin (LOM), the only process occurring is defluorination (from position 6 for the first two drugs, from position 8 for the last one). The quantum efficiency is both structure and medium dependent (4 close to 0.5 both in water and in 0.1 M phosphate buffer for LOM,‐ 0.01 for ENX and 0.004 for NOR in buffer, but more than an order of magnitude higher in neat water). Ofloxacin (OFL) is less light sensitive φ 0.001) and undergoes, in part, reactions different from defluorination. The photoreaction involves heterolytic C‐F bond fragmentation and its efficiency is determined by the internal charge‐transfer character of the excited state (increasing in the series OFL < NOR < ENX < LOM according to the electronegativity of the substituent in position 8) and by the stabilization of the resulting aryl cation (larger for the 8‐cation than for the 6‐cation). The relevance of these data for the rationalization of the known phototoxicity of these drugs is discussed.
Light Dose and Time Dependency of Photodynamic Cell Membrane Damage
Authors: Saito Takashi , Hartell Nick A. , Muguruma Hitoshi , Hotta Shu , Sasaki Satoshi , Ito Masao , Karube Isao 
Published: January 2008

AbstractWe have investigated the light dose and time dependency of photodynamic cell membrane damage using electrophysiological methods. This study controls the level of cell membrane damage by precisely administration of the light dose. The photosensitizer used was 5′,5″‐bis(aminomethyl)‐2,2′:5′,2″‐terthiophene dihydrochloride (BAT). A confocal laser scanning microscope was used to provide rapid light activation (<1 s) and the subsequent membrane damage was monitored using standard patch clamp techniques. In the presence of 49 μM BAT, light levels less than 0.94 J/cm2 led to a reversible depolarization (20 mV) and reduction of resistance (10%) within 3 s of illumination. Higher intensities of illumination (1.57 J/cm2) caused a complete and irreversible loss of membrane potential and cell membrane resistance within 8 s of illumination. The threshold dose of light required to induce cell death by illumination in the presence of BAT was increased in the presence of the antioxidant Trolox‐C.
The Complexity of the Prto PfrPhototransformation Kinetics Is an Intrinsic Property of Native Phytochrome*
Authors: Schmidt Peter , Gertsch Thomas , Remberg Anja , Gärtner Wolfgang , Braslavsky Silvia E. , Schaffner Kurt 
Published: January 2008

AbstractSeveral possible origins of the complex phytochrome red to far‐red light‐absorbing phytochrome (PrPfr) phototransformation kinetics in the nanosecond‐to‐second time range have been examined. Heterogeneity based on protein sequence is ruled out as an origin of the multi‐component kinetics because recombinant 124 kDa oat phytochrome A apoprotein reconstituted with phytochro‐mobilin and the native protein are very similar in this regard throughout this time range. The Prforms of native 124 kDa oat phytochrome A and of a homogeneous recombinant 65 kDa chromoprotein fragment exhibit thermochromic properties interpreted as arising in each case from the presence of two Prspecies in thermal equilibrium. They exhibit identical photochemical properties. The complex kinetics therefore cannot result from Prheterogeneity either. Thus, the presence of two Prforms in equilibrium (Pr,675and Pr,655) and the complex multiex‐ponential PrPfrphototransformation kinetics observed in all time ranges are intrinsic properties of the homogeneous holoprotein of oat phytochrome A.