bluuebunny/crossref_metadata_2025 huggingface dataset:
UV‐Induced Changes in Cell Cycle and Gene Expression within Rabbit Lens Epithelial Cells
Authors: Sidjanin Duska , Grdina David , Woloschak Gayle E.
Published: January 2008

Abstract— Damage to lens epithelial cells is a probable initiation process in cataract formation mediated by UV radiation. In these experiments, we investigated the effects of exposure to 254 nm radiation on cell cycle progression and gene expression in the rabbit lens epithelial cell line N/N1003A. The RNA was harvested at various times following exposure to UV (254 nm) radiation and analyzed by dot‐blot and northern blot hybridizations. These results revealed that during the first 6 h following exposure of the cells to UV, there was, associated with decreasing dose, a decrease in accumulation of transcripts specific for histones H3 and H4 and an increase in the in RNA encoding protein kinase C and β‐ and γ‐actin. Using flow cytometry, we detected an accumulation of cells in G1/S phase of the cell cycle 1 h following exposure to 254 nm radiation. The observed changes in gene expression, especially the decreased accumulation of histone transcripts reported here, may play a role in UV‐induced inhibition of cell cycle progression.
A Comparative Kinetic Analysis of the Flavin‐Photosensitized Oxidation and Reduction of Plastocyanin and Cytochrome c6 from Different Organisms
Authors: Navarro José A. , Hervás Manuel , Gutiérrez‐Merino Carlos , De la Rosa Miguel A.
Published: January 2008

Abstract— Laser flash photolysis spectroscopy has been used to investigate the kinetics of oxidation and reduction of pho‐tosynthetic plastocyanin (Pc) and cytochrome c6 (Cyt) from the cyanobacteria Anabaena PCC 7119 and Syne‐chocystis PCC 6803 by lumiflavin, riboflavin and flavin mononucleotide (FMN). For both redox reactions similar steric and electrostatic effects were observed with Syne‐chocystis proteins and Anabaena Cyt, thus suggesting that the same (or closely adjacent) sites are being used for electron entry and removal. In the case of Anabaena Pc, however, both the steric and electrostatic effects suggest that FMN‐dependent protein oxidation and reduction may occur at different sites, that is oxidation at the hydrophobic patch and reduction at the hydrophilic one. Kinetic pKa values of 5.8 and 6.2 have been determined for the lumiflavin‐dependent reduction of Anabaena and Monoraphidium Pc, respectively, whereas the oxidation reactions appear to be pH independent. Not only the reduction kinetics but also protein tyrosine fluorescence quenching by iodide ions suggest the occurrence of pH‐induced conformational changes in Pc. In conclusion, kinetic and fluorescent studies indicate that there are considerable quantitative similarities between Cyt and Pc when isolated from the same organism, consistent with the identical physiological role that these two proteins play inside the cells.
Synthetic Zinc and Magnesium Chlorin Aggregates as Models for Supramolecular Antenna Complexes in Chlorosomes of Green Photosynthetic Bacteria
Authors: Tamiaki Hitoshi , Amakawa Masaaki , Shimono Yoshiyuki , Tanikaga Rikuhei , Holzwarth Alfred R. , Schaffner Kurt
Published: January 2008

Abstract— A comparison of the spectra of in vitro (3‐hydroxymethyl‐131‐oxometallochlorin) and in vivo chlorosomal (bacterio‐chlorophyll‐c) aggregates suggests a similar supramolecular structure for the artificial oligomers and the bacte‐riochlorophyll‐c aggregates in the extramembranous antenna complexes (chlorosomes) of green photosynthetic bacteria. Synthetic zinc and magnesium chlorins have been found to aggregate in 1 % (vol/vol) tetrahydrofuran and hexane solutions and in thin films to form oligomers with the Qy absorption bands shifted to longer wavelengths by about 1900 (Zn chlorins) and 2100 cm−1 (Mg) relative to the corresponding monomer bands. Visible absorption and circular dichroism spectra of various zinc chlorins establish that a central metal, a 31‐hydroxy and a 131‐keto group are functional prerequisites for the aggregation. Vibrational bands measured by IR spectroscopy of solid films reveal two characteristic structural features of the oligomers: (1) a five‐coordinated metallochlorin macrocycle with an axial ligand (bands at 1500‐1630 cm−1), and (2) a hydrogen bond between the keto oxygen of one chlorin and the hydroxy group of a second chlorin, the oxygen of which is chelated to the metal atom of a third molecule, i.e. C=O…H‐O…M (=Zn or Mg).
Tumor Oxygenation Changes Post‐Photodynamic Therapy
Authors: Chen Q. , Chen H. , Hetzel F. W.
Published: January 2008

Abstract— Tumor oxygenation after a photodynamic therapy (PDT) treatment is a critical factor for understanding the post‐treatment metabolic pathway of the tumor. It also provides important information for designing combination therapy of PDT and other oxygen‐dependent anticancer modalities. In this study, mammary carcinoma in flank and hind leg of C3H mice were subjected to PDT at either subcurative or curative level (12.5 mg/kg Photofrin; 200 or 600 J/cm2, respectively). The before and post‐PDT tumor oxygenation was measured with an oxygen‐sensitive microelectrode. The data revealed that tumor oxygenation at the time of PDT has a profound effect on posttreatment tumor oxygenation, which may largely be due to an interplay between direct PDT cytotoxicity and PDT damage to the tumor microvasculature. Transient reoxygenation occurred after PDT, which may provide a window for improved combination therapy for other oxygen‐dependent modalities.
Synthesis and Photoreaction of 5‐Aikenyloxypsoralen Derivatives
Authors: Giménez‐Arnau Elena , Lepoittevin Jean‐Pierre
Published: January 2008

Abstract— In order to investigate the intramolecular “quenching” of the photoexcitation of some 5‐alkenyloxypsoralen derivatives, we have prepared model compounds in which a psoralen moiety was linked at position 5 to a terminal double bond via a polymethylenic chain of various length (n = 2‐9). The isolation and characterization of photocycloadducts obtained for each compound after irradiation at 365 nm in a polar solvent was performed. The results on the photoreactivity of this series of compounds show that the 3,4‐pyrone double bond of 5‐alkoxypsoralens is the most reactive. Four kinds of intramolecular photocycloadducts between the 3,4‐pyrone double bond and the chain unsaturation were obtained according to the length of the linking chain: cis‐syn, trans‐syn, cis‐anti and trans‐anti. Their structures were established by a combination of 1H and 13C NMR and fully assigned by lH NOE (nuclear Overhauser effect) and 1H‐13C HMQC (heteronuclear multiquantum correlation) spectroscopies. No traces of 4′,5′ adducts were detected.
Plant Responses to Changing Environmental Stress: Cyclobutyl Pyrimidine Dimer Repair in Soybean Leaves
Authors: Sutherland Betsy M. , Takayanagi Shinnosuke , Sullivan Joe H. , Sutherland John C.
Published: January 2008

Abstract— We have determined the capacity of soybean seedlings to repair DNA damage by UV doses that do not produce apparent injury in the plants. They remove cyclobutane pyrimidine dimers by both excision and photoreactiva‐tion. The rates and relative contributions of these repair processes were determined as a function of initial level of cyclobutyl pyrimidine dimers. Photoreactivation was detected in seedlings at all initial dimer levels. Although excision was not observed at the lowest dimer frequencies, at higher initial dimer levels it was quite effective in dimer removal. The rates of repair in soybean were substantially higher than in alfalfa seedlings at the same DNA damage levels.
Comparative Time‐Resolved Photosystem II Chlorophyll a Fluorescence Analyses Reveal Distinctive Differences between Photoinhibitory Reaction Center Damage and Xanthophyll Cycle‐Dependent Energy Dissipation*
Authors: Gilmore Adam M. , Hazlett Theodore L. , Debrunner Peter G. , Govindjee
Published: January 2008

Abstract— The photosystem II (PSII) reaction center in higher plants is susceptible to photoinhibitory molecular damage of its component pigments and proteins upon prolonged exposure to excess light in air. Higher plants have a limited capacity to avoid such damage through dissipation, as heat, of excess absorbed light energy in the PSII light‐harvesting antenna. The most important pho‐toprotective heat dissipation mechanism, induced under excess light conditions, includes a concerted effect of the trans‐thylakoid pH gradient (ΔpH) and the carotenoid pigment interconversions of the xanthophyll cycle. Co‐incidentally, both the photoprotective mechanism and photoinhibitory PSII damage decrease the PSII chlorophyll a (Chi a) fluorescence yield. In this paper we present a comparative fluorescence lifetime analysis of the xanthophyll cycle‐ and photoinhibition‐dependent changes in PSII Chi a fluorescence. We analyze multifrequency phase and modulation data using both multicomponent exponential and bimodal Lorentzian fluorescence lifetime distribution models; further, the lifetime data were obtained in parallel with the steady‐state fluorescence intensity. The photoinhi‐bition was characterized by a progressive decrease in the center of the main fluorescence lifetime distribution from ∼2 ns to ∼0.5 ns after 90 min of high light exposure. The damaging effects were consistent with an increased nonra‐diative decay path for the charge‐separated state of the PSII reaction center. In contrast, the ΔpH and xanthophyll cycle had concerted minor and major effects, respectively, on the PSII fluorescence lifetimes and intensity (Gilmore et ah, 1996, Photosynth. Res., in press). The minor change decreased both the width and lifetime center of the longest lifetime distribution; we suggest that this change is associated with the ΔpH‐induced activation step, needed for binding of the deepoxidized xanthophyll cycle pigments. The major change increased the fractional intensity of a short lifetime distribution at the expense of a longer lifetime distribution; we suggest that this change is related to the concentration‐dependent binding of the deepoxidized xanthophylls in the PSII inner antenna. Further, both the photoinhibition and xanthophyll cycle mechanisms had different effects on the relationship between the fluorescence lifetimes and intensity. The observed differences between the xanthophyll cycle and photoinhibition mechanisms confirm and extend our current basic model of PSII exciton dynamics, structure and function.
Alternation in Photosynthetic Characteristics ofAnabaena doliolumFollowing Exposure to UVB and Pb
Authors: Rai L. C. , Tyagi Bipul , Mallick Nirupama
Published: January 2008

Abstract—Anabaena doliolum, when exposed to either ultraviolet‐B (UVB) radiation or Pb, showed reduced growth rate, carbon fixation, O2‐evolution, photosynthetic electron transport activity and ATP pool size. The rate of respiration was found to increase in UVB‐treated cells; this increase was more pronounced in the cells exposed to UVB and Pb simultaneously. The UVB‐induced inhibition of 2,6‐dichlorophenol indophenol (DCPIP) photoreduction and lowering of chlorophyllafluorescence could not be reversed by artificial electron donors (diphenyl carbazide, NH2OH and MnCl2). These electron donors, however, substantially reversed the inhibition caused by Pb, thereby suggesting that UVB primarily inhibits the photosys‐tem II (PS II) reaction center and Pb arrests the electron flow at the water splitting site. Nevertheless, the suppressed fluorescence intensity and the reduced emission and excitation peaks of phycobilisomes indicate the involvement of Pb in inhibition of PS II. All combinations of UVB and Pb inhibited the different metabolic processes in a synergistic manner.
Detection of Early Stages of Carcinogenesis in Adenomas of Murine Lung by 5‐Aminolevulinic Acid‐Induced Protoporphyrin IX Fluorescence
Authors: Campbell D. L. , Gudgin‐Dickson E. F. , Forkert P. G. , Pottler R. H. , Kennedy J. C.
Published: January 2008

Abstract— Administration of the heme precursor 5‐aminolevulinic acid (ALA) leads to the selective accumulation of the photosensitizer protoporphyrin IX (PpIX) in certain types of normal and abnormal tissues. This phenomenon has been exploited clinically for detection and treatment of a variety of malignant and nonmalignant lesions. The present preclinical study examined the specificity of ALA‐induced porphyrin fluorescence in chemically induced murine lung tumors in vivo. During the early stages of tumorigenesis, ALA‐induced PpIX fluorescence developed in hyperplastic tissues in the lung and later in early lung tumor foci. In early tumor foci, maximum PpIX fluorescence occurred 2 h after the administration of ALA and returned to background levels after 4 h. There was approximately a 20‐fold difference in PpIX fluorescence intensity between tumor foci and the adjacent normal tissue. The specificity of ALA‐induced fluorescence for hyperplastic tissues and benign tumors in lung during tumorigenesis suggests a possible use for this fluorochrome in the detection of premalignant alterations in the lung by fluorescence endoscopy. Two non‐small cell lung cancer cell lines developed ALA‐induced PpIX fluorescence in vitro. These lines exhibited a light‐dose‐dependent phototoxic response to ALA photodynamic therapy (PDT) in vitro. Because PpIX is a clinically effective photosensitizer for a wide variety of malignancies, these results support the possible use of ALA‐induced PpIX PDT for lung cancer.
Measurement of Tumor Vascular Damage in Mice with 99m Tc‐MIBI Following Photodynamic Therapy
Authors: Brasseur Nicole , Lewis Karina , Rousseau Jacques , van Ller Johan E.
Published: January 2008

Abstract— The clinical perfusion agent 99mTc‐MIBI was used to monitor changes in tumor vascular perfusion (TVP) induced by Photofrin® (Pll)‐mediated photodynamic therapy (PDT). BALB/c mice bearing an EMT‐6 tumor on each hind thigh were given an intravenous injection of 1, 2 or 5 mg kg−1 PII. Twenty‐four hours later, one tumor was illuminated (600–650 run, 200 mW cm−2 400 J cm−2) while the other served as a control. At various time intervals after PDT (0, 2 and 24 h) mice received an intravenous injection of 99mTc‐hexakismethoxy(sobutyusonitri‐le (MIBI) (0.18 MBq g−1) and were sacrificed 2 min later. The light‐treated and the untreated tumors were then dissected, the radioactivity was counted and the percentage of the injected dose per gram of tumor (%ID g−1) was calculated as a measure of TVP. We observed that TVP is drug dose dependent, develops progressively with time post‐PDT and is inversely related to PDT efficacy. Our data show that early tumor retention of 99mMIBI is a simple method to assess TVP and vascular damage induced by PDT.
Liposome‐Mediated Delivery of Photosensitizers: Localization of Zinc (11)‐Phthalocyanine within Implanted Tumors after Intravenous Administration
Authors: Love W. G. , Duk S. , Biolo R. , Jori G. , Taylor P. W.
Published: January 2008

CGP55847, liposomal zinc(II)‐phthalocyanine (Zn‐Pc), was administered by the intravenous route to Swiss mice bearing intramuscularly implanted Ehrlich carcinomas or to C57BL6 mice bearing subcutaneously implanted B16 melanomas. Tumors were removed 3 h or 24 h after dosing and the intratumoral distribution determined by fluorescence microscopy. Localization of the photosensi‐tizer occurred more rapidly in the Ehrlich carcinoma than in the B16 melanoma; this difference in photosen‐sitizer uptake may be related to a higher degree of vas‐cularization of the carcinoma. The photosensitizer was found in association with blood vessels at 3 h but not 24 h after dosing and appeared to have a greater affinity for areas of tissue necrosis within the tumor compared to viable tumor tissue. Little or no Zn‐Pc was detected in the muscle tissue invaded by the Ehrlich carcinoma and was associated with membranes and the cytosol, but not the nucleus, of cells in both tumors.
The Photochemistry of the Retinoids as Studied by Steady‐State and Pulsed Methods
Authors: Dillon James , Gaillard Elizabeth R. , Bilski Piotr , Chignell Colin F. , Reszka Krzysztof J.
Published: January 2008

The retina and retinal pigment epithelium contain a number of retinoids in a metabolic pathway that eventually forms the visual pigments. This study investigates the photochemistry of those retinoids that may contribute to light‐induced damage to the retina. These include retinal (RAL), retinol (ROL), retinylpalmitate (ROLpal) and the protonated Schiff‐base of retinal (RAL.,). Their photochemistry was followed by both EPR spin‐trapping techniques and the direct detection of singlet oxygen via its luminescence at 1270 nm. Irradiation (>300 nm) of RAL, ROL in methanol (MeOH) or RALpal in dimeth‐ylformamide, produces free radicals from both solvents. Illumination of RAL., in MeOH containing NADH with light above 400 nm (and even above 455 nm) generates the superoxide radical. We also determined that the quantum yields for singlet oxygen sensitization by RAL, ROL or RALpal in MeOH are 0.05, 0.03 and 4.01, respectively. These values are at least 75% less than those previously found using chemical methods. These observations indicate that a major photochemical process for these retinoids may be an electron (or hydrogen) process that will lead to radical products, and that the singlet oxygen mechanism is of relatively minor importance in protic solvents. These results may explain the action spectra obtained from light‐induced damage to the retina.
Separating Enthalpy and Volume Contributions in Photothermal Experiments: A Perspective
Authors: Zimmt Matthew B. , Vath Peter A.
Published: January 2008

Abstract— Signals in photothermal experiments originate from both enthalpies and volumes of reaction. Two methods have been reported through which enthalpy and volume contributions can be separated: (1) analysis of signals as a function of temperature in aqueous solution or (2) analysis of signals from a series of linear alkanes or solvent mixtures. This manuscript describes potential difficulties in the application of the latter method to charge transfer reactions and proposes two alternative approaches by which the separation might be effected in a single organic solvent: (a) measurement of signals in isotopomeric solvents or (b) measurement of thermally induced changes in refractive index under conditions of constant density. The utility of neither approach has been demonstrated in any solvent other than water.
Resolving Component Overlap in Multiwavelength Kinetic Spectroscopy: Application to Raman Scattering from Intermediates in Triplet‐State Photoreactions
Authors: Fister Julius C. , Harris Joel M.
Published: January 2008

Abstract— Understanding of reaction mechanisms in photochemistry is advanced both by kinetic measurements to determine rates of reaction and by spectroscopic studies of the structures of precursors and photoproducts. When kinetics and spectroscopy are combined in a time‐resolved, multiwavelength spectroscopic measurement on a reacting system, spectra and structures of intermediates can also be determined. In this paper, the application of multidimensional least‐squares and factor analysis techniques for resolving overlapped spectra from intermediates in photochemical kinetics are discussed. The methods are employed specifically to resolve Raman spectra of intermediates in triplet‐state photoreactions. By varying excitation intensity, spectra of excited‐triplet states are resolved from ground states and solvent. By varying the concentration of a triplet quencher in the sample, the Raman spectrum of a sensitizer excited state (benzophe‐none) can be resolved from those of acceptor‐triplet states or radical photoproducts. Applications of these concepts in other areas of photochemical kinetics are addressed.
Two‐Photon Excitation of 4'‐Hydroxymethyl‐4,5',8‐Trimethylpsoralen
Authors: Oh Dennis H. , Stanley Robert J. , Lin Michelle , Hoeffler Warren K. , Boxer Steven G. , Berns Michael W. , Bauer Eugene A.
Published: January 2008

Abstract— Psoralens are a class of pharmaceutical agents commonly used to treat several cutaneous disorders. When irradiated with a mode‐locked titanium: sapphire (Ti: sapphire) laser tuned to 730 nm, an aqueous solution of 4'‐hydroxymethyl‐4,5',8‐trimethylpsoralen (HMT) emits blue light. The emission spectrum is centered at 452 nm and is identical to that obtained by one‐photon excitation with UVA excitation, and its magnitude depends quad‐ratically on the intensity of laser excitation. These results suggest that two‐photon excitation occurs to a potentially photochemically active state. To estimate the two‐photon absorption cross section, it was first necessary to measure the emission quantum yield of HMT using 365 nm excitation at room temperature that resulted in a value of 0.045 ± 0.007. The two‐photon absorption cross section of HMT at 730 nm is therefore estimated to be 20 ± 10−50 cm4 s (20 Göppert‐Mayer). The excited‐state photophysics and photochemistry of psoralens suggest potential applications to cutaneous phototherapy in diseases such as psoriasis and dystrophic epidermolysis bullosa.
The Role of Calcium in UVB‐lnduced Damage in Irradiated Ocular Lenses
Authors: Hightower Kenneth , McCready Janet
Published: January 2008

Abstract— The purpose of this study was to evaluate the role of altered calcium homeostasis in the development of irreversible membrane damage in the UVB‐irradiated ocular lens. In particular, experiments were designed to determine whether restricting calcium influx could prevent membrane damage that typically leads to ion imbalances and lens opacification following short‐term exposure to ultraviolet light (UVB). The influx of calcium was reduced by culturing lenses in a low‐calcium culture medium containing 0.3 mM Ca2+ rather than physiological concentrations of 1.6 mM. This low‐calcium protocol retarded calcium accumulation in UVB‐irradiated lenses for 2 days of culture, and opacification was delayed by 24 h. Loss of transparency did occur during the second day of culture, but more slowly than in irradiated lenses cultured in normal‐calcium medium. Membrane damage was assessed by evaluating loss in cation transport activity, assessed by measuring 86Rb uptake into cultured lenses. Uptake was markedly inhibited in UVB‐irradiated lenses and low‐calcium culture did not prevent this inhibition of cation transport, a finding that explains why low‐calcium protocol did not help maintain sodium homeostasis in irradiated lenses. Inhibition of cation transport and sodium accumulation eventually caused lens hydration and light scattering during extended culture in the absence of significant calcium elevation. Additional experiments were done to establish whether initial damage sustained by membranes could be repaired through the biosynthesis of new membrane proteins. Incorporation of 14C‐histidine in membranes of the UVB‐exposed lens was measured to assess membrane synthesis essential for repairing membrane damage. The rate of membrane protein synthesis, assessed by measuring incorporation of labeled amino acids, declined in UVB cataract, despite the prevention of calcium accumulation. These results suggest that one explanation for irreversible gain in sodium and calcium content accompanying opacification is the inability of lenses to replenish damaged membrane proteins comprising ion channels or transporters.
ICAM‐1 mRNA Levels and Relative Transcription Rates Are Decreased by UV Irradiation of Monocytes
Authors: Luca Dennis J. De , Trefzer Uwe , Tubesing Karen A. , Elmets Craig A.
Published: January 2008

Abstract— We have previously demonstrated that in vitro exposure of antigen‐presenting cells to UVB radiation inhibits their ability to activate T cells through selective effects on the expression of the adhesion molecule ICAM‐1 (intercellular adhesion molecule‐1). Intercellular adhesion molecule‐1 is an important costimulatory molecule provided by antigen‐presenting cells for T‐cell activation. Using human peripheral blood monocytes and the U937 human monocytoid cell line as model antigen‐presenting cells, we investigated the effect of UV radiation on the mRNA steady‐state levels for human ICAM‐1 by northern blot analysis and relative transcription rates of ICAM‐1‐speciflc mRNA by nuclear run‐on assay (NRO). Northern blot analysis demonstrated a decreased level of ICAM‐1 mRNA at 4 h postradiation relative to glyceraldehyde‐3‐dehydrogenase mRNA. The NRO analysis demonstrated a greater than 35% decrease of newly synthesized specific mRNA at 4 h postirradiation. The results demonstrate a transcriptionally based mechanism for the diminution of both mRNA and translatable mRNA specific for ICAM‐1 regulation in UV‐treated antigen‐presenting cells.
Quercetin Prevents UV‐lnduced Local Immunosuppression, but Does Not Affect UV‐lnduced Tumor Growth in SKH‐1 Hairless Mice
Authors: Steerenberg P.A. , Dortant J. Garsser V.P. , van de Vliet H. , Geerse L. , Verlaan A. P. J. , Goettsch W. , Sontag Y. , Norval M. , Gibbs N. K. , Bueno‐de‐Mesquita H. B. , Loveren H. Van
Published: January 2008

Abstract— Ultraviolet is thought to induce skin tumors by its dual activity as a mutagenic agent and a suppressor of cell‐mediated immunity. In the present study the effects of quercetin, a flavonoid‐containing compound, on carcinogenesis and immunosuppression were studied in SKH hairless mice exposed to suberythemal doses of UV for up to 17 weeks. It was found that quercetin did not affect the onset or growth of non‐melanoma skin tumors resulting from UV exposure. In contrast, it prevented the suppression in contact hypersensitivity (CHS) to picryl chloride induced by UV. The mechanism of this prevention might be explained by the observation that the decreased number of epidermal Langerhans'cells is partly prevented by the quercetin. Quercetin did not alter the effects of UV in increasing numbers of spleen and lymph node cells, only partly in decreasing the CD8‐positive cells in spleen cell populations and decreasing the lym‐phoproliferative response of spleen cells to the mitogens concanavalin A and phytohemagglutinin. Thus oral quercetin did not prevent UV‐induced carcinogenesis although it restored the skin‐associated CHS response probably by protecting the antigen‐presenting cells in the skin.
The Photodynamic Effect of Victoria Blue BO on Peripheral Blood Mononuclear and Leukemic Cells
Authors: Fiedorowicz Maciej , Pituch‐Noworolska Anna , Zembala Marek
Published: January 2008

Abstract— The photodynamic effect of Victoria blue BO (VB‐BO) and photoirradiation on peripheral blood mononuclear cells was studied. The cells were preincubated with VB‐BO followed by photoirradiation and overnight culture. The highest percentage of dead cells (propidium iodide assay in flow cytometry) was seen in the monocyte population. The lymphocytes showed a lower sensitivity to VB‐BO photodynamic action than the monocytes (12%vs 80% of Pi‐positive cells). The effect of VB‐BO and phototreatment on lymphocyte function was studied using a mitogen‐induced proliferation assay. A decrease of mitogen response was observed. The VB‐BO and photoirradiation were also used on leukemic cells. The leukemic cells from acute myeloid leukemia and B precursors leukemia were sensitive to VB‐BO photodynamic action. The high VB‐BO sensitivity of monocytes and leukemic cells (myeloid and lymphoid B derived) suggests possible application of VB‐BO for selective depletion of monocytes or sensitive leukemic cells.
Urocanic Acid Concentration and Photoisomerization in Caucasian Skin Phototypes
Authors: Snellman E. , Jansén C T. , Laihia J. K. , Milán T. , Koulu L. , Leszczynski K. , Pasanen P.
Published: January 2008

Abstract— To investigate the relationship between erythemal sensitivity of the skin to U V radiation and epidermal urocanic acid (UCA) concentration, 45 healthy volunteers of anamnestic skin phototypes (ASP) I‐IV were studied. In 16 of the subjects, we analyzed UCA photoisomerization after graded UVB exposures. The median and mean total UCA concentration in unirradiated skin was 22.4 and 35.3 nmol/cm2, and no statistically significant difference in total UCA concentrations was detectable either between ASP I through II and III through IV or between the phototested skin type (PSP) groups 1 through 2 and 3 through 4. The relative amount of the cis‐isomer varied between 3 and 35%, with median and mean values of 7 and 12%, respectively. No statistically significant difference in absolute or relative cis‐UCA concentrations was detectable between ASP I through II and III through IV, but a significantly lower absolute (P < 0.009) and relative (P < 0.002) cis‐UCA concentration in unirradiated skin was recorded in PSP groups 1 through 2, compared to types 3 through 4. In all tested subjects, an erythemally weighted dose of 1 mj/cm2sufficed to cause trans‐ to cis‐UCA isomerization. When comparing photosensitive (skin phototype I) and phototolerant (phototypes III and IV) individuals, who were irradiated with a reference 5 mJ/cm2UV dose or with fractions of 0.1‐1.0 of their individual minimal erythema dose values, no skin phototype‐dependent difference in ability to photoisomerize was discernible.
The Effect of Chronic Treatment of Mice with Urocanic Acid Isomers
Authors: El‐Ghorr Ali A. , Norval Mary
Published: January 2008

Abstract— Trans‐urocanic acid (trans‐UCA) accumulates in the upper layers of the epidermis and can be isomerized to cis‐UCA by UV light irradiation. Cis‐urocanic acid possesses immunosuppressive properties that have led to its consideration as one of the initiators of UV‐induced immunosuppression. High quantities of cis‐UCA persist in human skin for prolonged periods in the summer months. In the present study, mice were injected intradermaUy with trans‐UCA and cis‐UCA three times a week for 4 weeks in order to ascertain the long‐term effects of the presence of these compounds in the skin. The weight of mice and of their spleens were unaffected by the cis‐ or trans‐UCA treatment. A decrease in thymus weight, accompanied by an increase in lymph node weight, was detected in the cis‐UCA‐treated mice compared with trans‐UCA‐treated mice and untreated controls. A net accumulation of lymphocytes and dendritic cells (DC) in lymph nodes was evident following cis‐UCA treatment but the percentage of both CD4+and CD8+lymphocytes as well as Ia+DC remained constant among the different treatment groups, indicating that there was no specific migration or proliferation of a particular subset of cells. The in vitro lymphoproliferative response of lymph node cells to the mitogen concanavalin A was significantly sup pressed by cis‐UCA treatment. The density of Langerhans cells in the epidermis of the ears was not altered by the chronic cis‐UCA treatment. However, chronic cis‐UCA treatment did suppress the mixed skin lymphocyte reaction response utilizing epidermal cells from the ears (an uninjected area of skin), indicating a systemic suppression. Compared with trans‐UCA treatment, chronic cis‐UCA treatment did not cause a significant reduction in the contact hypersensitivity response to oxazolone or the delayed hypersensitivity response to herpes simplex virus. Thus, chronic treatment with cis‐UCA led to the suppression of some, but not all, of the immune parameters that are affected by UVB irradiation.
Factors Affecting M13 Bacteriophage Inactivation by Methylene Blue Photosensitization
Authors: Abe H. , Wagner S. J. , Kuwabara M. , Kamo N. , Ikebuchi K. , Sekiguchi S.
Published: January 2008

Abstract— We have investigated the factors that affect the virucidal activity of methylene blue (MB) photosensitization. The M13 bacteriophage was more rapidly inactivated at higher temperatures (6°C < 24°C < 38°C). Rate constants for inactivation were 0.072, 0.139 and 0.260 (log. inactiva‐tion)/(J/cm2) at 6°C., 24°C and 38°C., respectively. On the other hand, dye penetration into virus particles, which was monitored by the fluorescence of YOYO‐1, was unchanged with incubation temperature. These data suggest that temperature dependency of M13 inactivation was due to factors other than dye permeability. The pH of the virus suspension also affected the rate of M13 inactivation by MB. The M13 bacteriophage was inactivated faster in basic suspensions and slower in acidic suspensions compared with neutral buffers. These results suggest that temperature and pH are factors that influence the extent of MB photosensitization, and hence, the control of these factors will be necessary for MB phototreatment of plasma products in transfusion medicine.
Delivery of Benzoporphyrin Derivative, a Photosensitizer, into Atherosclerotic Plaque of Watanabe Heritable Hyperlipidemic Rabbits and Balloon‐Injured New Zealand Rabbits
Authors: Allison B. A. , Crespo M. T. , Jain A. K. , Richter A. M. , Hsiang Y. N. , Levy J. G.
Published: January 2008

Abstract— In this study we compared the plasma distribution and arterial accumulation of a photosensitizer, benzoporphyrin derivative (BPD), in two models of atherosclerosis: the spontaneous lesions of the Watanabe heritable hyperlipidemic (WHHL) rabbit and induced lesions of the balloon‐injured, cholesterol‐fed New Zealand white (NZW) rabbit. Selective uptake and retention of a photosensitizer by the abnormal portion of a vessel is a necessity in order for photodynamic therapy to become a successful modality for inhibition of intimal hyperplasia, selective removal of atherosclerotic tissue or imaging of diseased arteries. Liposome‐based formulations were compared to freshly isolated native low density lipoprotein (LDL) and acetylated‐LDL (Ac‐LDL) as delivery vehicles for BPD. Plasma distribution of the photosensitizer was analyzed by KBr density gradient ultracentrifuga‐tion. Although the delivery vehicle influenced plasma distribution immediately postinjection, BPD subsequently partitioned according to the plasma concentration of the lipoproteins. Photosensitizer level in plaque and normal artery specimens was determined by ethyl acetate extraction and spectrofluorometric measurement. The measurement of BPD in normal and atherosclerotic arterial tissue demonstrated a selective accumulation in atherosclerotic tissue. Preassociation with LDL and Ac‐LDL enhanced accumulation of BPD in atherosclerotic tissue when compared with normal artery (mean ratios of 2.8 and 4.1 were achieved, respectively). These results indicate that the preferential uptake of BPD by atherosclerotic plaque can be enhanced by preassociation with plasma lipoproteins, suggesting that light activation could lead to a highly selective destruction of diseased vascular tissue.
The Photodynamic Action of Methylene Blue on the Ion Channels of Paramecium Causes Cell Damage
Authors: Saitow Fumihito , Nakaoka Yasuo
Published: January 2008

Abstract— The photodynamic effects of methylene blue (MB) on wild‐type and mutant strains of Paramecium Were studied. From measurements of survival and cell motility under the continuous application of light in the presence of MB, the mutant strains remained alive for about three times longer than the wild‐type strain. Although the resting potential of the mutant cells was similar to that of wild‐type cells, the continuous photodynamic action shifted the membrane potentials of the mutant and wild‐type cells to a depolarized level and a hyperpolarized level, respectively, from that before light application. Under voltage clamping, the mutant cells reduced not only the outward current elicited by the photodynamic action but also the outward tail current elicited by the preceding pulse of hyperpolarization. We conclude that the mutant strain is defective in the activation of Ca2+‐dependent K+channels. This defect might cause a reduction in the Ca2+influx because of the suppression of the membrane hyperpolarization, which results in the elongation of survival time under the photodynamic action.
Localization of Blepharismin Photosensors and Identification of a Photoreceptor Complex Mediating the Step‐up Photophobic Response of the Unicellular Organism, Blepharisma
Authors: Matsuoka Tatsuomi , Sato Mie , Maeda Mitsuru , Naoki Hideo , Tanaka Takaharu , Kotsuki Hiyoshizo
Published: January 2008

Abstract— Photosensitivity for the step‐up photophobic response of Blepharisma is localized in the anterior 1/5 of the cell body. Blepharismin pigment, which is believed to be a photoreceptor pigment mediating the step‐up photophobic response of the cells, was separated into five types of blepharismin (BL‐1, ‐2, ‐3, ‐4 and ‐5). Blepharismin‐1, ‐3, ‐4 and ‐5 were localized in the posterior 4/5, while BL‐2 was located over the entire cell body; the anterior end, which is the photosensitive region, contained only BL‐2. The results indicate that a functional photoreceptor pigment mediating the step‐up photophobic response is BL‐2. Hydroxylapatite chromatography revealed that BL‐2 was bound to a 200 kDa membrane protein. We concluded that a photoreceptor mediating the step‐up photophobic response was a BL‐2/200 kDa protein complex.
Evidence for Signal Transduction in the Stimulation of Nitrate Uptake by Blue Light in Chlorella saccharophila*
Authors: Mätschke M. , Riedel J. , Tischner R.
Published: January 2008

Abstract— In Chlorella saccharophila blue light supplementary to red light stimulated the nitrate uptake rate by a factor of two. This stimulation was independent of photosynthesis as it occurred in cells where photosynthesis was totally inhibited by DCMU. The effect of blue light (2 min 25 μE m −2 s−1 are sufficient) led to an event that persisted for 50 min (memory effect) as an enhanced nitrate uptake. However, the addition of ocadaic acid extended the effect of blue light over 90 min. Blue light alone also led to the phosphorylation of distinct proteins (120 kDa and 34 kDa) bound to the plasma membrane with that at 34 kDa being the most prominent. This phosphorylation was inhibited by staurosporine and was stimulated after the plasma membrane vesicles were treated with several freeze‐thawing cycles.
Reorientational Motions of the D96N and T46V/D96N Mutants of Bacteriorhodopsin in the Purple Membrane
Authors: Harms Greg S. , Johnson Carey K.
Published: January 2008

Abstract— The reorientational motions of the D96N and T46V/D96N mutants of bacteriorhodopsin in purple membrane have been investigated by time‐resolved linear dichroism measurements. The reorientations in the early stages of the photocycle are identical to those observed in wild‐type bacteriorhodopsin: anisotropics of photocycle intermediates in both D96N and T46V/D96N are rK= 0.38±0.01, rL= 0.35±0.01, rM= 0.35±0.01. The anisotropy of the initial state, rBR, exhibits decays to zero in D96N and to negative values in T46V/D96N on the time scale of tens of milliseconds. This anisotropy decay can be explained by a model that involves the motion of unexcited or spectator proteins adjacent to a photocycling protein. The amplitude and time constants of spectator reorientational motion are similar to those that have been observed in the wild type. Contributions from the anisotropy of the N‐state were detected in measurements of the T46V/D96N mutant, in which a large N‐state population accumulates. The value of rN is estimated to be 0.30±0.05 in T46V/D96N.
Fluorescent Molecular Probes II. The Synthesis, Spectral Properties and Use of Fluorescent Solvatochromic Dapoxyl Dyes
Authors: Diwu Zhenjun , Lu Yixin , Zhang Cailan , Klaubert Dieter H. , Haugland Richard P.
Published: January 2008

Abstract— 2,5‐Diphenyloxazoles that embody a dimethylamino group at position 4 of the 5‐phenyl ring and a sulfonyl group at position 4 of the 2‐phenyl ring were prepared as new fluorescent solvatochromic dyes. In these molecules, there is a “push‐pull” electron transfer system from the 5‐phenyl moiety to the 2‐phenyl ring. These compounds show strong solvent‐dependent fluorescence that is well correlated with the empirical solvent polarity parameter ET (30). The solvent polarity dependence suggests that the fluorescence arises from an intramolecular charge transfer. The fluorescence‐environment dependence, long emission wavelength, large extinction coefficients, high fluorescence quantum yields and large Stokes shift of the fluorophores can be used to develop ultrasensitive fluorescent molecular probes to study a variety of biological events and processes.
Development of Refractoriness of Induced Human Heme Oxygenase‐1 Gene Expression to Reinduction by UVA Irradiation and Hemin
Authors: Noel Alexandre , Tyrrell Rex M.
Published: January 2008

Abstract— Using primary human fibroblasts we have observed the existence of an acquired refractoriness of the heme oxygenase‐1 gene to induction by a second dose of UVA (320‐380 nm) radiation. We studied the kinetics of development of refractoriness over a time interval of up to 72 h between the first inducing event and the second (challenge) dose. Complete refractoriness was observed at 48 h. We also studied development of refractoriness after UVA, sodium arsenite and H2O2 treatment in all possible combinations and demonstrated that only UVA led to refractoriness. Ultraviolet radiation induced partial refractoriness to H2O2 induction but did not change the response to sodium arsenite. In an investigation of the mechanism of development of refractoriness we used the heme oxygenase inhibitor, tin‐protoporphyrin IX and showed that induction of heme oxygenase enzymatic activity is a crucial step. However, the induction of ferritin, which is known to play a key role in protection against oxidative stress, did not appear to be involved. Damage to membranes is also probably not involved in the refractoriness mechanism. Because either hemin alone or UVA radiation are able to lead to a refractoriness of the heme oxygenase‐1 gene to reinduction by a second exposure to one or the other agent in human fibroblasts, we conclude that heme, or an as yet unidentified heme derivative, is involved in the refractoriness response.
Action Spectrum for Induction of Promoter Activity of Phenylalanine Ammonia‐Lyase Gene by UV in Carrot Suspension Cells
Authors: Takeda Junko , Ozeki Yoshihiro , Yoshida Kazuichi
Published: January 2008

Abstract— The full‐length promoter (−2335) of the carrot (Daucus carota) phenylalanine ammonia‐lyase gene (gDcPALl) fused to the luciferase reporter gene was transiently transformed to carrot protoplasts by electroporation, and the promoter activity induced by monochromatic UV light of various wavelengths was examined. The action spectrum constructed from the fluence–response curves showed a single peak at around 280 nm, suggesting that the activation of the gDcPALl promoter is categorizable as one of the UVB light responses. The same assay system was applied to variously truncated gDcPALl promoters and to CaMV35S promoter fusion with various parts 5′‐upstream of the gDcPALl promoter. The region from ‐396 to ‐190 (relative to the transcription start site) fused to the CaMV35S core (‐90) promoter showed a 280 nm‐dominant response. However, gDcPALl promoters truncated above ‐570 and ‐396, although they contain the region between ‐396 and ‐190, did not show such a typical UVB response, i.e. they responded to 260 nm light as much as to 280 nm light. The promoter truncated to below ‐190 also responded to 260 nm light as much as to 280 nm light. Therefore we assumed that the gDcPALl promoter is composed of three functionally different parts: the upstream above ‐570 (modulator), the region from ‐396 to ‐190 (UVB responsive) and the downstream below ‐190 (UVB and C responsive). The overall UVB response of the gDcPALl full‐length promoter is explained as the result of interaction of these three components.
Effect of Acute Exposure to Hydrogen Peroxide on the Production of Phytoplankton and Bacterioplankton in a Mesohumic Lake
Authors: Xenopoulos Marguerite A. , Bird David F.
Published: January 2008

Abstract— Active oxygen species such as hydrogen peroxide are produced as a result of UV radiation interaction with natural organic matter and can build up to high concentrations in many aquatic environments. Although the resulting oxidizing potential may affect biological materials and processes, the ecological effects have not yet been studied in any detail. We examined the influence of hydrogen peroxide exposure on phytoplankton and bacterioplankton production in Lac Cromwell, a small humic lake in the Laurentian Hills (Quebec, Canada). A range of hydrogen peroxide concentrations were added to natural samples that were incubated in situ; results indicate that even small amounts of added hydrogen peroxide (50 nM inhibited bacterial production in this lake. A 100 nM addition inhibited bacteria by as much as 40%. On the other hand, low concentrations of added hydrogen peroxide usually stimulated photosynthesis. Catalase addition to eliminate hydrogen peroxide from water usually stimulated bacterial production but had no effect on algal carbon fixation. If these results represent true changes in growth rate, they indicate very different sensitivities of phytoplankton and bacteria to oxidative stress.
Photodynamic Treatment of Red Blood Cell Concentrates For Virus Inactivation Enhances Red Blood Cell Aggregation: Protection with Antioxidants
Authors: Ben‐Hur Ehud , Barshtein Gregory , Chen Shuqi , Yedgar Saul
Published: January 2008

Abstract— Photodynamic treatment (PDT) using phthalocyanines and red light appears to be a promising procedure for decontamination of red blood cell (RBC) concentrates for transfusion. A possible complication of this treatment may be induced aggregation of RBC. The production of RBC aggregates was measured with a novel computerized cell flow properties analyzer (CFA). The PDT of RBC concentrates with sulfonated aluminum phthalocy‐anine (AIPcS4) and the silicon phthalocyanine Pc 4 under virucidal conditions markedly enhanced RBC aggregation and higher shear stress was required to disperse these aggregates. The clusters of cells were huge and abnormally shaped, unlike the rouleaux formed by untreated RBC. This aggregation was prevented when a mixture of antioxidants was included during PDT. Addition of the antioxidants after PDT reduced aggregation only partially. It is concluded that inclusion of antioxidants during PDT of RBC concentrates prior to transfusion may reduce or eliminate the hemodynamic risk that the virucidal treatment may present to the recipient.
On the Influence of Higher Excited States on the ISC Quantum Yield of Octa‐aL‐alkyloxy‐substituted Zn‐Phthalocyanine Molecules Studied by Nonlinear Absorption
Authors: RuUckmann Ilja , Zeug Andre , Herter Ralph , Roder Beate
Published: January 2008

Abstract— Octa‐aL‐alkyloxy‐substituted Zn‐phthalocyanines are an interesting class of far red‐absorbing photosensitizers. The chemical structure, the calculated steric conformation, the observed linear optical properties and an anomalous luminescence from a higher than S, excited state are reported. To study the optical properties of higher excited states and their occupation dynamics up to delay times of 15 ns we have carried out measurements of transient absorption spectra after 14 ps pulsed, resonant B‐band and Q‐band excitation. From these measurements the excited state singlet‐singlet and triplet‐triplet spectra as well as the intersystem crossing (ISC) quantum yields are obtained. The main result is an excitation wavelength‐dependent ISC quantum yield that can be explained by an additional ISC channel between higher excited singlet and triplet states. The large rate of this channel is justified by the resonance between higher triplet states, observed in the triplet‐triplet spectrum and the B, absorption band. Using kinetic model calculations, a lifetime of the higher excited singlet state of some picoseconds is predicted and the influence of a two‐step absorption process on the population density of this higher excited singlet state is discussed.
Two‐Photon Resonance‐Enhanced Transients in Femtosecond Spectra of Molecular Aggregates
Authors: Gaizauskas E. , Feller K.‐H.
Published: January 2008

Abstract— Two‐photon resonance‐enhanced four‐wave mixing processes relevant to pump‐probe difference absorption measurements with femtosecond pulses in linear aggregates were analyzed theoretically. Transitions to two‐exciton bands were found to be contributing to coherent transients of the time‐resolved spectra around the zero delay time. This part of the signal provides in principle the possibility of direct measurement of the exciton delocalization length.