bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRANSMISSION OF HUMAN EPIDERMIS AND STRATUM CORNEUM AS A FUNCTION OF THICKNESS IN THE ULTRAVIOLET AND VISIBLE WAVELENGTHS
Authors: Bruls Wiel A. G. , Slaper H. , Van Der Leun Jan C. , Berrens L. 
Published: January 2008

AbstractThe dependence of radiation transmission on sample thickness was studied in isolated samples of human stratum corneum and full‐thickness epidermis. The investigation also included samples of skin repeatedly exposed to UV‐B. Transmission was measured in the ultraviolet and in the visible from 248–546 nm. Two methods, one microscopic and the other mechanical, were used to measure thickness. There was a good correlation between the results.The dependence of transmission on thickness in these samples could be described satisfactorily by an exponential function, implying that the Lambert‐Beer law is approximately valid. Thus, a single parameter, such as the half‐value layer (d½), is sufficient to characterize absorption in the skin samples.Water content of the isolated stratum corneum was influenced by maintenance conditions: samples floating on water containing a small amount of NaCl were more hydrated than samples floating on a more concentrated salt solution, or stored in air. Changes in water content of the samples resulted in changes of thickness and, to a lesser extent, of transmission. Approximatein vivovalues ofd½were computed after estimating thein vivowater content of stratum corneum.Differences found in the shape of the transmission spectra of stratum corneum and full‐thickness epidermis may reflect differences in chemical composition. The influence of wetting of the skin on its sensitivity to sunlight is explained in a new way.
PHOTODYNAMIC RELEASE OF PROTOPORPHYRIN FROM INTACT ERYTHROCYTES IN ERYTHROPOIETIC PROTOPORPHYRIA: THE EFFECT OF SMALL REPETITIVE LIGHT DOSES
Authors: Brun Atle , Sandberg Sverre 
Published: January 2008

Abstract— Erythrocytes from patients with erythropoietic protoporphyria contain large amounts of protoporphyrin bound to (hemo)globin. Irradiation of these cells causes a shift in fluorescence emission maximum and a decreased fluorescence intensity which is consistent with transfer of protoporphyrin from (hemo)globin to the cell membrane. When the erythrocytes were irradiated intermittently, nearly 70% of the protoporphyrin was released and the hemolysis was less than 3%. Giving the total light dose as a single pulse, resulted in 84% protoporphyrin release and 16% hemolysis. In vivo the erythrocytes obtain small, repetitive light doses when circulating in the dermal capillaries. We suggest the possibility that in patients with erythropoietic protoporphyria these small light pulses could be sufficient to photodamage the binding place of protoporphyrin on (hemo)globin. In the dark, protoporphyrin can then move from (hemo)globin through the cell membrane and bind to albumin in the serum. Our findings indicate that if protoporphyrin is not present in the cell membrane during irradiation, no photohemolysis will occur. This may explain why patients with erythropoietic protoporphyria have no abnormal hemolysis. The effect of intermittent light pulses may also contribute to the understanding of the protoporphyrin release from erythrocytes in patients with erythropoietic protoporphyria.
INACTIVATION OF PHAGE BY NEAR‐ULTRAVIOLET RADIATION AND HYDROGEN PEROXIDE
Authors: Eisenstark A. , Buzard R. L. , Hartman P. S. 
Published: January 2008

AbstractA series of phage with different genomes (both single‐stranded and double‐stranded RNA and DNA) was inactivated with hydrogen peroxide (H2O2) in various combinations with far‐ultraviolet (FUV) and near‐ultraviolet (NUV) radiations. In every case but one (a lipid‐coated phage), a sublethal H2O2 concentration greatly enhanced killing by NUV but not FUV. Moreover, this NUV/H2O2 synergism was oxygen independent and there was little if any host cell reactivation upon NUV plus H2O2 inactivation. These results suggest that these phage are inactivated by a common mechanism irrespective of nucleic acid composition, but that some phage genomes may be more vulnerable to NUV/H2O2 inactivation than others.
PHOTOINITIATED DNA DAMAGE BY MELANOGENIC INTERMEDIATES IN VITRO
Authors: H. Koch Walter , Chedekel Miles R. 
Published: January 2008

AbstractCysteinyldopas, metabolic by‐products of activated melanocytes, are photochemically unstable in the presence of biologically relevant ultraviolet radiation (i.e. wavelengths > 300 nm). Initial photochemical processes involve free radical production; continued photolysis yields polymeric photoproducts. Radicals produced during 5SCD photolysis were trapped by 5,5‐dimethyl‐l‐pyrrolidine‐l‐oxide (DMPO) and identified by their ESR spectra. Further characterization by use of nitroso spin trap (2‐methvl‐2‐nitrosopropane‐MNP) demonstrated that homolytic cleavage of the ‐S‐CH2 bond of the 5SCD cysteinyl side chain is a significant photochemical pathway. The potential photobiological significance of these reactive intermediates was investigated in vitro using isolated nucleic acids. Radiolabeled 5‐[35S]‐cysteinyldopa was found to photobind to calf thymus DNA with 300 nm light activation. Under similar conditions, 5‐S‐cysteinyldopa also induced single strand breakage of 3H‐radiolabeled superhelical, circular pBR322 plasmid DNA. The implications of the 5SCD photoinitiated DNA damage and the production of highly reactive free radicals in this process are discussed with respect to the etiology of various skin cancers, particularly malignant melanoma.
PHOTOLYTIC DEGRADATION OF IBUPROFEN. TOXICITY OF THE ISOLATED PHOTOPRODUCTS ON FIBROBLASTS and ERYTHROCYTES
Authors: Castell J. V. , Gomez‐L. M. J. , Miranda M. A. , Morera I. M. 
Published: January 2008

AbstractThe photodegradation of Ibuprofen, a widely used non‐steroidal anti‐inflammatory drug (NSAID), was examined. Several photoproducts (I‐VI) were isolated and identified on the basis of their IR‐1H‐NMR‐ and 13C‐NMR‐ spectra. The chemical structures were confirmed by unambiguous alternative synthesis from available reagents. The most significant primary photochemical process was the cleavage of the C‐C bond a to the carboxy group. Subsequent secondary processes (hydrogen abstraction, dimerization, incorporation of methanol, or reaction with oxygen) might account for the formation of the different photoproducts. The cytotoxic effects were assayed using the red‐blood cell lysis test and the enzyme leakage (LDH and GOT) from cultured fibroblasts. Compound V [l‐(4 isobutylphenyl)‐ethanol] was found to be toxic for both system at concentrations greater than 1 mM while compound IV [l‐(4 isobutylphenyl acetophenone)] was toxic for fibroblasts but not for erythrocytes at the same concentration. Ibuprofen and the other photocompounds were apparently non‐toxic. The significance of these results is discussed in connection with the possible in vivo phototoxicity of Ibuprofen.
PHOTOELECTRIC EFFECTS IN BILAYER LIPID MEMBRANE CONTAINING METALLO‐PORPHYRINS and DYES
Authors: Kutnik Jan , Tien H. Ti 
Published: January 2008

AbstractThe bilayer lipid membrane (BLM) system containing metallo‐porphyrins (M‐TPP) and dyes as photosensitizers and electron mediators was studied. Cyclic voltammetry was used to determine photoconductivity and photo‐emf of the system. The largest photoconductivity was observed for the Mg‐TPP containing BLM with methyl viologen (MV2+) and iodine (I2) present in the aqueous solution. Photoactive dyes, due to their redox ability caused photovoltage up to 30 mV to develop, but no conductance change was observed under illumination in absence of Mg‐TPP. The relevance of cyclic voltammetry to the photoconductance and the photo‐emf observed in the BLM is discussed.
AUGMENTATION OF ULTRAVIOLET ERYTHEMA BY INDOMETHACIN IN ACTINIC PRURIGO: EVIDENCE OF MECHANISM OF PHOTOSENSITIVITY
Authors: Farr P. M. , Diffey B. L. 
Published: January 2008

Abstract— The effect of topical indomethacin on the intensity of erythema induced by ultraviolet radiation was measured by reflectance spectrophotometry in six patients with actinic prurigo. The intensity of UV‐C erythema was decreased by indomethacin in five patients. The intensity of UV‐B erythema was increased by indomethacin in five patients, and UV‐A erythema was increased by indomethacin in all patients. The increased inflammatory response induced by UV‐B and UV‐A with indomethacin application was related to erythemal sensitivity at these wavelengths. Topical indomethacin caused no change in the intensity of UV‐A erythema in a group of non‐photosensitive subjects.That inhibition of cyclo‐oxygenase augments the inflammatory response to ultraviolet radiation suggests that lipoxygenase metabolites of arachidonic acid may be involved in the mechanism of photosensitivity in actinic prurigo.
TIME‐GATED FLUORESCENCE SPECTROSCOPY OF THE TUMOR LOCALIZING FRACTION OF HpD IN THE PRESENCE OF CATIONIC SURFACTANT
Authors: Cubeddu R. , Ramponi R. , Liu W.‐Q. , Docchio F. 
Published: January 2008

Abstract—Time‐gated fluorescence spectroscopy was performed on the tumor localizing fraction (TLF) of HpD in buffer at different concentrations of cationic surfactant. This technique obtains emission spectra with programmable delay relative to the excitation pulse. According to the measured fluorescence decay‐time constants (0.7, 3 and 15 ns) three gates were considered, delayed by 0, 5 and 18 ns, respectively, to evaluate the contribution of the emitting molecular species to the spectra. Simultaneous to these measurements, fluoresence decay waveforms and time‐integrated spectra were also detected. In buffer and in detergent micelles the fluorescence spectra are given by the superposition of the emission of the different molecular species present in the solution, and no appreciable interaction among the chromophores is observed. On the contrary, in the pre‐micellar range of the surfactant, evidence for the existence of an energy transfer mechanism was found. This effect seems to be related to the conflgurational state of the TLF polymeric chains and depends on the relative TLF/surfactant concentration.
CRITICAL IMPORTANCE OF THE TRIPLET LIFETIME OF PHOTOSENSITIZER IN PHOTODYNAMIC THERAPY OF TUMOR
Authors: Takemura T. , Ohta N. , Nakajima S. , Sakata I. 
Published: January 2008

Abstract—The relation between the lifetimes of the triplet states of various porphyrins and their photosensitizing effects on the photodynamic therapy (PDT) of tumor has been examined. Diethylene‐triamine pentaacetic acid ester of 4‐[1‐(2‐hydroxy‐ethyloxy)ethyl]‐2‐vinyl deuteroporphyrin‐IX gallium (III) complex (Ga‐DP), zinc (II) complex (Zn‐DP), and manganese (III) complex (Mn‐DP) and Photofrin II (PII) are used as the photosensitizer. The triplet lifetimes have been measured for the samples adsorbed on filter paper (FP) and found to be 57 ms (Ga‐DP), 26 ms (Zn‐DP), 610 |xs (Mn‐DP) and 9 ms (PII). The phosphorescence of Ga‐DP in tumor‐bearing golden hamsters are measured both in tumor tissue and in liver. They show bi‐exponential decay with the lifetimes of about 5 and 20 ms. From the values, the generation rate, kct[3O2], of singlet molecular oxygen in living animal tissue may be estimated to be an order of 102 s‐1. The PDT effects have been quantitatively investigated for in vitro experiments; upon irradiation the growth inhibitions of mouse p388 leukemia cells are obtained as a function of concentration of Ga‐DP, Zn‐DP, Mn‐DP and PII. The experimental results indicate that the PDT effects depend essentially on the triplet lifetimes of the photosensitizers.
CYTOTOXICITY AND MUTAGENICITY OF OPHTHALMIC SOLUTION PRESERVATIVES AND UVA RADIATION IN L5178Y CELLS
Authors: Withrow Thomas J. , Brown Natalie T. , Hitchins Victoria M. , Strickland Amparo G. 
Published: January 2008

Abstract—Four chemical preservatives commonly used in ophthalmic solutions were tested for their toxic and mutagenic potential in mouse lymphoma cells with and without exposure of the cells to ultraviolet A (UVA) radiation. The preservatives tested were benzalkonium chloride (BAK), chlorhexidine, thimerosal and ethylenediaminetetraacetic acid (EDTA). Cell survival and mutagenesis were measured using the L5178Y mouse lymphoma (TK+/‐) system. Cells were exposed to varying amounts of preservatives for 1 h at 37o.C, and then aliquots were irradiated with UVA radiation (during the exposure to preservative). Cells were then assayed for survival, and for mutagenesis at the thymidine kinase (TK) locus. In concentrations commonly found in ophthalmic solutions, BAK, chlorhexidine, and thimerosal were toxic to cells, and thimerosal was slightly mutagenic. When cells were exposed to preservative and UVA radiation, chlorhexidine was mutagenic and the mutagenic activity of thimerosal was enhanced.
SINGLET OXYGEN INDUCES FRANK STRAND BREAKS AS WELL AS ALKALI‐ AND PIPERIDINE‐LABILE SITES IN SUPERCOILED PLASMID DNA
Authors: BLAZEK ED ROBERT , PEAK JENNIFER G. , PEAK MEYRICK J. 
Published: January 2008

AbstractA covalently closed, circular, supercoiled plasmid was exposed to singlet oxygen by a separated‐surface sensitizer. For each exposure, the quantity of single oxygen entering the DNA target solution was estimated by its oxidation of histidine. After singlet oxygen exposure, some DNA samples were treated to disclose occult lesions. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed circular and linear species, and all bands were quantitated fiuorometrically. Exposure of supercoiled plasmid DNA to singlet oxygen induced frank DNA strand breaks, alkali‐labile sites (pH 12.5, 90°C, 30 min), and piperidine‐labile sites (0.4 M, 60°C, 30 min), all in a dose‐dependent manner. Yields of alkali‐labile and piperidine‐labile sites ranged from one to four times the frank strand break yield. Replacement of buffered H2O by buffered D2O as the DNA solvent for singlet oxygen exposures increased DNA lesion yields by a factor of 2.6 (averaged over lesion classes). Our data for the detection of frank strand breaks is at variance with published results from studies in which singlet oxygen was derived from a thermolabile endoperoxide dissolved in the DNA solution.
BIOLOGICAL UV‐DOSES AND THE EFFECT OF AN OZONE LAYER DEPLETION
Authors: DAHLBACK ARNE , HENRIKSEN THORMOD , LARSEN SøREN H. H. , STAMNES KNUT 
Published: January 2008

AbstractEffective UV‐doses were calculated based on the integratated product of the biological action spectrum (the one proposed by IEC, which extends to 400 nm, was adopted) and the spectral irradiance. The calculations include absorption and scattering of UV‐radiation in the atmosphere, both for normal ozone conditions as well as for a depleted ozone layer.For Scandinavian latitudes the effective annual UV‐dose increases by approximately 4% per degrees of latitude towards the Equator. An ozone depletion of one percent increases the annual UV‐dose by approximately 1% at 60°N (increases slightly at lower latitudes). A large depletion of 50% over Scandinavia (60°N) would give these countries an effective UV‐dose similar to that obtained, with normal ozone conditions, at a latitude of 40°N (California or the Mediterranean countries). The Antarctic ozone hole increases the annual UV‐dose by 20 to 25% which is a similar increase as that attained by moving 5 to 6 degrees of latitude nearer the Equator.The annual UV‐dose at higher latitudes is mainly determined by the summer values of ozone. Both the ozone values and the effective UV‐doses vary from one year to another (within ± 4%). No positive or negative trend is observed for Scandinavia from 1978 to 1988.
KINETIC MODEL OF BACTERIORHODOPSIN PHOTOCYCLE: PATHWAY FROM M STATE TO bR
Authors: CHERNAVSKII D. S. , CHIZHOV I. V. , LOZIER R. H. , MURINA T. M. , PROKHOROV A. M. , ZUBOV B. V. 
Published: January 2008

AbstractA model of the last parts of the bacteriorhodopsin (bR) photocycle is proposed on the basis of experimental data for the kinetic behavior of the ‘O’ intermediate during a temperature pulse in distilled water suspension. The model includes the previously proposed (but not well characterized) intermediate ‘N’ between the ‘M’ and ‘O’ states of bR. This intermediate exists in fast temperature‐dependent quasistationary equilibrium with the red‐shifted intermediate ‘O’ and has a maximum of absorption close to the bR spectrum.
PRODUCTION OF MALONALDEHYDE FROM SQUALENE, A MAJOR SKIN SURFACE LIPID, DURING UV‐IRRADIATION
Authors: DENNIS K. JASON , SHIBAMOTO TAKAYUKI 
Published: January 2008

AbstractMalonaldehyde (MA), a product of lipid peroxidation, is known to have a number of toxicological effects. Among skin surface components, squalene has been suggested as a significant source of MA following UV exposure. Irradiation of squalene coated on the inside surface of glass tubes served as a simple model to examine skin surface photochemistry. Malonaldehyde produced during UV‐irradiation was reacted with methyl hydrazine to form N‐methylpyrazole, which was then measured by gas chromatographic analysis. Ultraviolet A‐irradiation produced low levels of MA from squalene, with a maximum of 1.0 nmol MA/µmol squalene near 6 h. Malonaldehyde production varied with the energy of irradiation, with levels of 176 nmol/mg squalene and 9 nmol/mg squalene produced after 3 h of irradiation with UVB and UVA, respectively. The thiobarbituric acid (TBA) assay for lipid peroxidation showed large overestimations of MA levels under all irradiation conditions tested. The TBA assay predicted the highest levels of MA with UVC but we did not detect any MA with our assay.
SKIN PHOTOSENSITIVITY AND PHOTODESTRUCTION OF SEVERAL POTENTIAL PHOTODYNAMIC SENSITIZERS
Authors: ROBERTS W. GREGORY , SMITH KEVIN M. , MCCULIOUGH JERRY L. , BERNS MICHAEL W. 
Published: January 2008

Abstract— The major side effect associated with porphyrins (Photofrin II) in clinical photodynamic therapy is skin photosensitivity. In order to avoid this deleterious reaction, patients must remain out of the sunlight for approximately 1 month. A possible procedure to reduce the amount of skin photosensitivity is to photodegrade (photobleach) the compound in the skin.In this study, we report a series of experiments describing the photodegradation rates of two photosensitizers currently receiving attention due to their potential for use in PDT (mono L‐aspartyl chlorin e., and chloroaluminum sulfonated phthalocyanine). These compounds are compared to Photofrin II (Pfll). Experiments consisted of determining photodegradation rates and efficiencies of the sensitizers in (i) phosphate buffered saline (PBS), (ii) PBS with fetal calf serum (to enhance absorption and simulate cellular binding or deaggregation), (iii) Chinese Hamster Ovary cells, and (iv) Balb/c mice. We performed two standardized skin sensitivity assays using the Hartely albino guinea pig irradiated with a UV blue point lamp and Balb/c mice irradiated with the therapeutic wavelength of each sensitizer. In addition, we performed a cell clonogenicity assay comparing photodegraded and fresh Pfll on CHO cells. The photodegraded Pfll exhibited significant phototoxicity, although the fluorescence was bleached by more than 70%.The results show that Pfll causes major skin photosensitization and that the other compounds produce no substantial skin sensitivity. Our studies suggest that photodegradation of Pfll with 630 nm light has little influence on the phototoxicity of the compound. In addition, skin sensitivity was not alleviated with prior photobleaching with 405 nm light.
A FLUORESCENCE STUDY OF THE BINDING OF HOECHST 33258 and DAPI TO HALOGENATED DNAs
Authors: Hard Torleif , Fan Pei , Kearns David R. 
Published: January 2008

Abstract— We have studied the time‐resolved and the steady‐state fluorescence of the DNA groove binders 4',6‐diamidino‐2‐phenylindole (DAPI) and Hoechst 33258 with the double stranded DNAs poly(dA‐dU) and poly(dl‐dC) and their halogenated analogs, poly(dA‐FdU) and poly(dI‐Br5dC). These studies were prompted by earlier observations that the steady‐state fluorescence of Hoechst 33258 is quenched on binding to halogenated DNAs (presumably due to an intermolecular heavy atom effect involving the halogen atom in the major groove), and recent studies which clearly point to a binding site in the minor groove of DNA. Measurements of the time resolved fluorescence decay demonstrate that the fluorescence of Hoechst 33258 is quenched on binding to the halogenated DNAs. in agreement with previous observations. However, quenching studies carried out using the free halogenated bases IdUrd and BrdCyd in solution yielded bimolecular rate constants more than one order of magnitude larger than those expected for an intermolecular heavy atom effect. Moreover, the quenching of the Hoechst 33258 fluorescence was accompanied by an accelerated photochemical destruction of Hoechst 33258. We therefore conclude that the fluorescence quenching observed with halogenated DNAs is probably due to a photochemical reaction involving Hoechst 33258, rather than direct contact of Hoechst 33258 with the halogen substituents in the major groove of the DNA. The fluorescence decay measurements however, do provide clear evidence for at least two different modes of binding. Taking into account the alternating sequences used in this study and the possibility of two different conformations for bound dye, at least four different modes of binding are plausible. Our present data do not allow us to distinguish between these alternatives.The time‐resolved fluorescence decays and fluorescence quantum yields of DAPI are not affected by the presence of the heavy atom substituents in the DNA major groove. Based on this observation and earlier reports that DAPI binds in one of the DNA grooves, we conclude that the high affinity sites for DAPI on DNA are located in the minor groove.
LIGHT‐DEPENDENT CAROTENOID BIOSYNTHESIS IN MUTANT C‐6D OF Scenedesmus obliquus
Authors: Humbeck Klaus 
Published: January 2008

Abstract— Pigment mutant C‐6D of the green alga Scenedesmus obliquus exhibits a light‐dependent chloroplast differentiation. The changes were analyzed by high performance liquid chromatography (HPLC). Dark‐grown cells of mutant C‐6D contain only precursors of carotenoids (carotene, neurosporene, lycopene and β‐zeacarotene). The lycopene and two neurosporenes were identified to be cw‐isomers. After transfer to light lycopene decreases rapidly. Simultaneously the other precursors increase for a short period and then decrease, too.Using a specific HPLC‐system the changes in carotene‐ and xanthophyll‐content were analyzed. During the first 30 min of illumination the amount of β‐carotene increases very fast and then levels off. The kinetics of xanthophyll‐formation differ remarkably. Whereas lutein is synthesized immediately after onset of illumination, all other xanthophylls are formed with high rates only after a lag‐phase of about 30 min.After illumination in the presence of nicotine no cyclic carotenes and xanthophylls could be detected. Instead of the cw‐lycopene these cells contain high amounts of the all‐trans lycopene.The light‐regulation of the biosynthetic pathway leading to carotenes and xanthophylls in mutant C‐6D is discussed.
PHOTOCHEMICAL ONE‐POT SYNTHESIS OF VINBLASTINE and VINCRISTINE
Authors: Pennanen S. , Huhtikangas A. 
Published: January 2008

AbstractThe naturally occurring cytostatic dimer alkaloids vinblastine1and vincristine2were photochemically synthesized in slightly acidic aqueous solution from the monomer alkaloids catharan‐thine3and vindoline4. Multi‐centre reactions should obviously be involved and some of the principal photochemistry‐associated phenomena here discussed are quite likely to be characteristic even to the biosynthetic reactions yielding vinblastine1and vincristine2in the cells ofCatharanthus roseus.
NEW TRENDS IN THE DESIGN OF LUMINESCENT METAL COMPLEXES*
Authors: Balzani Vincenzo , Ballardini Roberto 
Published: January 2008

Abstract—The requirements needed for an ideal luminophore are discussed with reference to the luminescent properties of organic molecules and metal complexes. Recent strategies for the design of luminescent metal complexes are discussed, with particular emphasis on cage‐type complexes and oligonuclear homo‐ and hetero‐metallic complexes.