bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultraviolet Radiation in a High Mountain Lake of the Austrian Alps: Air and Underwater Measurements
Authors: Sommaruga Ruben , Psenner Roland
Published: January 2008

Global UV radiation was measured with a portable multichannel filter radiometer at the surface and underwater in a high mountain lake (2417 m above sea level) of the Austrian Alps during 16 days in summer 1995. During this period, total column ozone values that changed only by 34 Dobson units explained a significant part of the variability in UVB radiation at 305 nm as indicated by the negative correlation with the ratio 305:340 nm (rs= ‐0.810, P < 0.01). High radiation at the surface combined with high water transparency allowed substantial UVB radiation to reach the bottom of this lake. The diffuse attenuation coefficient for downward irradiance at 305 nm changed within 2 weeks from 0.24 m‐1 (10% at 9.6 m depth) to 0.32 m‐1 (10% at 7.2 m depth). This change in attenuation was related to the development of phytoplankton after the ice break‐up as indicated by a six‐fold increase in chlorophyll‐a concentrations during this period. Our results suggest that phytoplankton and/ or phytoplankton‐derived organic substances are important for the UV attenuation in this oligotrophic lake.
Effect of Dosimetric and Physiological Factors on the Lethal Photosensitization of Porphyromonas gingivalis in vitro
Authors: Bhatti Manpreet , MacRobert Alexander , Meghji Sajeda , Henderson Brian , Wilson Michael
Published: January 2008

The aims of this study were to (1) determine the effect of dosimetric and physiological factors on the lethal photosensitization of Porphyromonas gingivalis using tolui‐dine blue O (TBO) and light from a helium/neon (HeNe) laser; (2) determine the influence of sensitizer concentration, preirradiation time, serum and growth phase on sensitizer uptake by P. gingivalis. The dosimetric factors studied were concentration of TBO, light dose and preirradiation time. The physiological factors were presence of serum, pH and bacterial growth phase. Sensitizer uptake by P. gingivalis under various conditions was determined using tritiated TBO (3H‐TBO). In the presence of TBO, a light dose‐dependent increase in kill was attained (100% kill at 4.4 J). There was no significant effect on the numbers killed when TBO was increased from 12.5 to 50 µg/mL. An increase in preirradiation time gave slightly increased kills. High kills were achieved at all three pH (6.8–8.0). Although kills were substantial in the presence of serum, they were significantly less than those obtained in the presence of saline. Cells in all three growth phases were susceptible to lethal photosensitization, although stationary phase cells were slightly less susceptible. Maximum uptake of TBO occurred within 60 s and uptake in serum was less than in saline. The uptake by the log phase cells was greater at lower concentrations of sensitizer (50 µg/mL), compared to the other two phases.
The Subcellular Localization of Zn(ll) Phthalocyanines and Their Redistribution on Exposure to Light
Authors: Wood Simon R. , Holroyd J. Andrew , Brown Stanley B.
Published: January 2008

ABSTRACT
Dual Solvatochromism of Neutral Red
Authors: Singh M. K. , Pal H. , Bhasikuttan A. C. , Sapre A. V.
Published: January 2008

Abstract— The effect of solvent polarity on the electronic absorption and fluorescence properties of neutral red (NR), a phenazine‐based dye of biological importance has been investigated in several neat and mixed solvents. An unusual dual solvatochromic behavior has been observed that reveals the existence of two closely spaced electronic excited states in NR. In low‐polarity solvents the fluorescence of the NR is mainly emitted from the localized excited state, whereas in high‐polarity solvents the emission from the charge transfer state dominates. The dipole moments of the localized and charge transfer states of NR have been estimated from the solvatochromic shifts. The dipole moment of the localized excited state (4.8 D) is only slightly higher than that of the ground state (2.0 D), while that of the charge transfer state is drastically higher (17.5 D). Fluorescence quantum yields and the life‐times of NR have been determined in different solvents and correlated with the solvatochromic shifts.
Environmental Effects on Cellular Photosensitization: Correlation of Phototoxicity Mechanism with Transient Absorption Spectroscopy Measurements
Authors: Aveline Béatrice M. , Sattler Rose Marie , Redmond Robert W.
Published: January 2008

Abstract—Little is directly known about the influence of the local environment experienced by a photosensitizer in a biological system on its photophysics and photochemistry. In this paper, we have addressed this issue by correlating mechanistic studies using laser flash photolysis with cellular phototoxicity data, obtained under the same experimental conditions. In particular, we have focused on the interaction between local concentrations of photosensitizer (deuteroporphyrin) and oxygen in determining the mechanism of phototoxicity in L1210 cells. In cells, as well as in models such as liposomes and red blood cell ghosts, hypochromicity and a reduction in fluorescence and intersystem crossing yields are observed on increasing the photosensitizer concentration between 0.5 and 20 μM, which illustrates the onset of a self‐association. In aerated cellular preparations, the phototoxicity is predominantly type II (singlet oxygen) for all concentrations studied but an oxygen‐independent mechanism occurs at the higher concentrations in deaerated samples. These observations are readily explained by consideration of triplet state kinetics as a function of oxygen and photosensitizer concentrations in cells. The rate constant for quenching of the photosensitizer triplet state by oxygen in cells was measured as 6.6 × 108M−1s−1and by photosensitizer ground state as ‐106M−1s−1(in terms of local concentration). The latter reaction gave rise to a long‐lived species that is presumably responsible for the oxygen‐independent phototoxicity observed at the higher photosensitizer concentrations used. This self‐quenching of the triplet state is postulated to arise from electron transfer resulting in radical ion formation. Under conditions where no self‐quenching contributes, the phototoxicity measured as a function of oxygen concentration correlates well with a model based on the determined kinetic parameters, thus, unambiguously proving the intermediacy of singlet oxygen. These effects should be borne in mind when interpreting phototoxicity mechanisms fromin vitrocell studies. The excellent correlation achieved between laser flash photolysis data and measured phototoxicity gives credence to the direct use of photophysical techniques to elucidate photochemical mechanisms in biological media.
Effects of Light Environment During Culture on UV‐lnduced Cyclobutyl Pyrimidine Dimers and Their Photorepair in Rice (Oryza sativa L.)
Authors: Kang Hye‐Sook , Hidema Jun , Kumagai Tadashi
Published: January 2008

Abstract— We examined the effects of a light environment during culture of rice plants (Oryza sativa) on the steady‐state cyclobutyl pyrimidine dimer (CPD) level, CPD induction by challenge UVB exposure and the ability to photorepair CPD. The steady‐state CPD level in plants grown under visible radiation with supplemental UVB radiation in a growth chamber was several times higher than in plants grown without supplemental UVB radiation, whereas in outdoor‐grown plants, it was not enhanced by supplemental UVB radiation. The susceptibility to CPD induction by challenge UVB exposure was highest in dark‐grown plants and decreased with increasing irradiance of visible radiation at low and high levels and outdoors. Chronic UVB radiation reduced the susceptibility to UV‐induced CPD in plants grown both indoors and outdoors. There was a significant negative correlation between CPD levels induced by challenge UVB exposure and the content of UV‐absorbing compounds. The UV‐induced CPD could be reduced by subsequent blue radiation in all samples except in dark‐grown seedlings. The higher the irradiance of visible radiation in the culture, the greater the ability to photorepair CPD. Chronic UVB radiation did not increase the ability to photorepair CPD.
Ultrasonic Modulation of Scattered Light in Turbid Media and a Potential Novel Tomography in Biomedicine
Authors: Wang Lihong V.
Published: January 2008

Ultrasonic modulation of scattered laser light was used to image objects buried in tissue‐simulating turbid media. The ultrasonic wave focused into the turbid media modulated the laser light passing through the ultrasonic field. The modulated laser light collected by a photomultiplier tube reflected primarily the local mechanical and optical properties in the zone of ultrasonic modulation. A raster scanning over a heterogeneous turbid medium yielded an image of the medium based on the ultrasound‐modulated optical signal. The detectability of modulated signal was estimated using diffusion theory. The dependence of the modulated signal on the off‐axis distance of the detector from the optic axis and on the amplitude of ultrasound was studied. The mechanisms of ultrasonic modulation of scattered light are discussed. A theory based on the field autocorrelation function is reviewed as well.
Potential Mechanisms of Photodynamic Inactivation of Virus by Methylene Blue I. RNA–Protein Crosslinks and Other Oxidative Lesions in Qβ Bacteriophage
Authors: Schneider J. Edward , Tabatabaie Tahereh , Maidt Lindsay , Smith Renee Horning , Nguyen Xuan , Pye Quentin , Floyd Robert A.
Published: January 2008

A spectrum of oxidative lesions was observed in a bacteriophage‐based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Qβ were exposed to methylene blue plus light (MB+L), inactivating events, or "hits" occurred that were oxygen‐dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8‐oxo‐7,8‐dihydroguanine (8‐oxoGua), and (3) single‐strand breaks (ssb) in the RNA genome and (4) RNA‐protein crosslinks. Formation of carbonyl groups associated with protein in the Qβ phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Qβ genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full‐length Qβ RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8‐oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB+L, crosslink formation between Qβ RNA and protein was observed by virtue of the location of RNA at the interface of phenol‐aqueous extractions of phage suspensions. A significant increase over background of RNA‐protein complexes (including full‐length Qβ RNA) was observed at the lowest concentration of MB tested (0.5 μM), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Qβ inactivation and its expected lethality, RNA‐protein crosslink formation may be important as an inactivating lesion in bacteriophage Qβ following MB+L exposure.
The Effect of Fluence Rate on Tumor and Normal Tissue Responses to Photodynamic Therapy
Authors: Sitnik Theresa M. , Henderson Barbara W.
Published: January 2008

Photodynamic therapy (PDT), carried out at low fluence rates, may enhance tumor response as well as affect treatment selectivity. We have studied the effects of fluence rate on the response of the murine radiation‐induced fibrosarcoma (RIF) to PDT using Photofrin® (5 mg/kg). Tumor response was tested over a large range of fluence rates (10‐200 mW/cm2) and fluences (25‐378 J/ cm2). Low fluence rates were more efficient; ‐60 J/cm2 at 10 mW/cm2 was needed to achieve the same tumor growth delay as ‐100 J/cm2 at 150 mW/cm2 and ‐150 J/cm2 at 200 mW/cm2. Despite this increased efficiency, lower fluence rates still required longer treatment times for equivalent anti‐tumor effects: 95 min for 57 J/cm2 at 10 mW/cm2versus 11 min for 100 J/cm2 at 150 mW/cm2. Effects of fluence rate on the PDT toxicity to normal tissue were examined through the response of the murine (C311) foot to Photofrin® PDT. Treatment with conditions that produced equivalent tumor responses, i.e. 57 J/cm2 at 10 mW/cm2 and 100 J/cm2 at 150 mW/cm2, resulted in a more severe foot response at the higher fluence rate (median peak response: 0.9 at 10 mW/cm2, 1.5 at 150 mW/cm2) with more time required for tissue to return to normal (8 days at 10 mW/cm2, at least 30 days at 150 mW/cm2). However, when feet were treated with an equal fluence of 100 J/cm2 at various fluence rates, longer healing times accompanied the lower fluence rate treatments. Overall, this paper demonstrates that lower PDT fluence rates are associated with increased efficiency of tumor response. If this increased efficiency is accounted for by lowering treatment fluence, lower fluence rates also may result in a more favorable normal tissue response to treatment.
Studies of the Energy Transfer among Allophycocyanin from Phycobilisomes of Polysiphonia urceolata by Time‐Resolved Fluorescence Isotropic and Anisotropic Spectroscopy
Authors: Zhang Jing‐min , Zheng Xi‐guang , Zhang Jian‐ping , Zhao Fu‐li , Xie Jie , Wang He‐zhou , Zhao Jing‐quan , Jiang Li‐jin
Published: January 2008

Abstract— The excitation energy transfer processes in the allophycocyanin (APC) monomer and trimer from phycobilisomes of Polysiphonia urceolata were studied using picosecond time‐resolved fluorescence isotropic and anisotropic spectroscopy. Based on our experimental results, conclusions could be drawn as follows: (1) After the processes of exciton localization are finished, the localized excitation energy on any chromophore can be transferred to the other chromophores due to the weak couplings between them, and the processes among three p84‐phycocyaninbilin (PCB) chromophores in the center of the ring shape of the APC trimer are more important than those of between a84‐ and p84‐PCB chromophores in the same monomer. (2) The decay time constants of 95 ± 5 ps and 40 ± 5 ps components, observed by us in this work, were assigned to the excitation energy transfer or redistribution between α84‐ and β84‐PCB chromophores in the same monomer of the APC trimer and among three β84‐PCB chromophores in the center of the ring shape of the APC trimer, respectively. Specifically, the assignment of the decay constants for the 40 ± 5 ps component was different from those of previous results. (3) Based on the model of Debreczeny, and using the fluorescence residual anisotropy r(∞) with a probing wavelength of 650 nm, the angles between the C3 symmetry axis and transition dipoles of α84‐ and ‐PCB chromophores were found to be φa84= 67° and φβ84= 148°, respectively, which are in agreement with the prediction of the X‐ray crystal structure of APC. (4) The results show that anisotropy decays, observed with the APC trimer, did exhibit a strongly probing wavelength dependence that did not show up in the monomer.
Photooxidation of Methionine Derivatives by the 4‐Carboxybenzophenone Triplet State in Aqueous Solution. Intracomplex Proton Transfer Involving the Amino Group
Authors: Hug Gordon L. , Bobrowski Krzysztof , Kozubek Halina , Marciniak Bronislaw
Published: January 2008

Abstract— Oxidation of the triplet state of 4‐carboxybenzophenone (CB) by a series of five substituted methionines and three methionine‐containing dipeptides was monitored under laser flash photolysis conditions in aqueous solution. Spectral resolution techniques were employed to follow the concentration profiles of the intermediates formed from the quenching events. From these concentration profiles, quantum yields for the intermediates were determined. Branching ratios were evaluated for the decay of the charge‐transfer complex by the competing processes of back electron transfer, proton transfer and escape of radical ions. The relative prominence of these processes was discussed in terms of the proton‐transfer tendencies of the nominal sulfur‐radical‐cationic species. A systematic decrease was observed in the quantum yields for the escape of radical ions along with a correlated increase in the proton‐transfer yields. The enhanced propensity of the sulfur radical cations to depro‐tonate is due to deprotonation at the carbons adjacent to the sulfur‐cationic site and at the unsubstituted amino groups when present. This scheme was supported by an observed decrease in the yields of dimeric sulfur radical cations with an increase in the electron‐withdrawing abilities of the substituents, making the radical‐cationic species stronger acids. The involvement of protons on the amino groups was implicated by the correlation of the quantum yields of ketyl radical formation in the photochemistry experiments with the rate constants for the reaction of the CB radical anion with the sulfur‐containing substrates in pulse radiolysis experiments.
Photophysical Properties of Tin Ethyl Etiopurpurin I (SnET2) and Tin Octaethylbenzochlorin (SnOEBC) in Solution and Bound to Albumin
Authors: Pogue Brian W. , Redmond Robert W. , Trivedi Niraj , Hasan Tayyaba
Published: January 2008

Abstract— The photophysical characteristics of two second‐generation PDT photosensitizers, tin ethyl etiopurpurin I (SnET2) and tin octaethylbenzochlorin (SnOEBC), have been measured in homogeneous solution and when bound to bovine serum albumin (BSA). The ground state and triplet state absorption spectra have been characterized, as have triplet lifetimes and quantum yields for intersys‐tem crossing, singlet oxygen formation and photobleaching. In total, these parameters provide a complete set of data that can be used to quantitatively compare the photosensitizing efficiencies of these molecules. The photo‐bleaching quantum yield of SnET2 is increased dramatically when it is bound to BSA, thus limiting the production of singlet oxygen at incident fluences above 1 J/cm2. In contrast, the quantum yield of photobleaching of SnOEBC is at least an order of magnitude lower than that of SnET2 under these conditions and does not significantly limit the photosensitization process for typical in vivo or in vitro fluences. This difference is expected to play a significant role in determining the relative photosensitizing ability of these compounds in vivo.
Chloroplast Biogenesis 81: Transient Formation of Divinyl Chlorophyll a Following a 2.5 ms Light Flash Treatment of Etiolated Cucumber Cotyledons
Authors: Adra Al Numan , Rebeiz Constantin A.
Published: January 2008

Abstract—The possible conversion of nascent divinyl (DV) chloro‐phyllide a (Chlidea) to DV chlorophylla(Chi a during the early stages of greening in a dark divinyl‐light divinyl‐light/dark divinyl (DDV‐LDV‐LDDV) plant species was investigated. Etiolated cucumber cotyledons (Cucu‐mis sativus L.) were subjected to a 2.5 ms light flash followed by darkness. The DV and monovinyl (MV) components of the protochlorophyllidea(Pchlidea), Chlidea, Pchlideaester and Chiapools were monitored quantitatively by high‐resolution spectrofluorometry, immediately following the light treatments and after various periods in darkness. The light treatment photoconverted DV and MV Pchlideato DV and MV Chlidea. Some photoconversion of MV Pchlide a ester to MV Chi a also appeared to take place. A sharp rise in the level of DV Chi a following the light treatment could not be accounted for by photoconversion of DV Pchlide a ester. It must have arisen by rapid esterification of nascent DV Chlide a. After illumination, the level of DV Chi a rose for 5 s and then declined. The implications of the transient rise and fall of DV Chiacontent following illumination to the Chiabiosynthetic heterogeneity is discussed.
Further Characterization of UVB Radiation Effects on Langerhans Cells: Altered Expression of the Costimulatory Molecules B7‐1 and B7‐2
Authors: Denfeld Ralf W. , Tesmann Jens P. , Dittmar Henning , Weiss Johannes M. , Schöpf Erwin , Weltzien Hans U. , Simon Jan C.
Published: January 2008

We have reported previously that low‐dose UVB radiation (UVBR, 50‐200 J/m2) perturbs the antigen‐presenting cell (APC) function of murine Langerhans cells (LC) by interfering with yet undefined costimulatory signals. In this study, we investigated (1) the effects of UVBR on the expression of the costimulatory molecules B7‐1 and B7‐2 on murine LC, (2) the functional consequences of defective B7‐1 and B7‐2 signalling on primary and secondary T‐cell responses induced by LC and (3) the mechanism by which UVBR interferes with B7‐1 and B7‐2 expression. Ultraviolet‐B radiation dose‐dependently inhibited the culture‐induced upregulation of B7‐1 and B7‐2 on LC from both UVB‐susceptible (UVBs, C57BL/6) and UVB‐resistant (UVBR, Balb/c) mice and abrogated their capacity to stimulate proliferation of naive alloreactive T cells and of the KLH (keyhole limpet hemocyanin)‐specific T helper (Th)1 clone HDK‐1. The UVBR‐induced suppression of B7‐1 and B7‐2 on LC and their perturbed APC function were related, because exogenous triggering of the B7/CD28 pathway with a stimulatory monoclonal antibody (mAb) for CD28 to UVB‐irradiated LC partially restored T‐cell proliferation. Such reconstitution was not observed when the mAb was added to killed LC, indicating that the UVBR‐induced suppression of APC function was not due to lethal effects on LC. Conditioned supernatants from UVB‐irradiated epidermal cells did not inhibit the functional upregulation of B7‐1 and B7‐2, suggesting that UVBR inhibits B7‐1 and B7‐2 upregulation by acting directly on LC and not by altering LC costimulatory function via release of soluble immunosuppressive factors. In conclusion, UVBR distorts the functional expression of B7‐1 and B7‐2 on LC from both UVBs and UVBR mice, thereby contributing to the failure of UVB‐irradiated LC to stimulate resting alloreactive T cells or KLH‐specific Thl cells.
Photomovement of the Gliding Cyanobacterium Synechocystis sp. PCC 6803
Authors: Choi Jong‐Soon , Chung Young‐Ho , Moon Yoon‐Jung , Kim Changhoon , Watanabe Masakatsu , Song Pill‐Soon , Joe Cheol‐O , Bogorad Lawrence , Park Young Mok
Published: January 2008

Abstract— Using a computerized videomicroscope motion analysis system, we investigated the photomovements of two Synechocystis sp. (PCC 6803 and ATCC 27184). Synechocystis sp. PCC 6803 displays a relatively slow gliding motion. The phototactic and photokinetic speeds of this cyanobacterium in liquid media were 5μm/min and 15.8 μm/min, respectively, at 3μmol/m2/s of stimulant white light. Synechocystis sp. PCC 6803 senses light direction rather than intensity for phototaxis. Synechocystis sp. ATCC 27184 showed a weak photokinesis but no phototaxis. Analysis of Synechocystis sp. ATCC 27184 suggests that the loss of phototaxis results from spontaneous mutation during several years of subculture. When directional irradiation was applied, the cell population of Synechocystis sp. PCC 6803 began to deviate from random movement and reached maximum orientation at 5 min after the onset of stimulant white light. Synechocystis sp. PCC 6803 showed high sensitivity to the stimulant white light of fluence rates as low as 0.002 |unol/m2/s. Neither 1,3‐dichlorophenyldimethyl urea nor cyanide affected phototactic orientation, whereas cyanide inhibited gUding speed. This result suggests that the phototaxis of Synechocystis sp. PCC 6803 is independent of photosynthetic phosphorylation and that its gliding movement is primarily powered by oxidative phosphorylation. In the visible wavelength region, 560 nm, 660 nm and even 760 nm caused positive phototaxis. However, 360 nm light induced strikingly negative phototaxis. Therefore, at least two independent photoreceptors may exist to control phototaxis. The photoreceptor for positive phototaxis appears likely to be a phytochrome‐like tetrapyrrole rather than chlorophyll a.
Inhibition of UV‐lnduced Immune Suppression and lnterleukin‐10 Production by Plant Oligosaccharides and Polysaccharides
Authors: Strickland Faith M. , Darvill Alan , Albersheim Peter , Eberhard Stefan , Pauly Marcus , Pelley Ronald P.
Published: January 2008

Abstract— Application of Aloe barbadensis poly/oligosaccharides to UV‐irradiated skin prevents photosuppression of delayed‐type hypersensitivity (DTH) responses in mice. We tested the hypothesis that these carbohydrates belong to a family of biologically active, plant‐derived polysaccharides that can regulate responses to injury in animal tissues. C3H mice were exposed to 5 kJ/m2 UVB from unfiltered FS40 sunlamps and treated with between 1 pg and 10 μg tamarind xyloglucans or control polysaccharides methylcellulose or dextran in saline. The mice were sensitized 3 days later with Candida albicans. Tamarind xylogiucans and purified Aloe poly/oligosaccharides prevented suppression of DTH responses in vivo and reduced the amount of interleukin (IL)‐IO observed in UV‐irradiated murine epidermis. Tamarind xyloglucans were immunoprotective at low picogram doses. In contrast, the control polysaccharides methylcellulose and dextran had no effect on immune suppression or cutaneous IL10 at any dose. Tamarind xyloglucans and Aloe poly/oligosaccharides also prevented suppression of immune responses to alloantigen in mice exposed to 30 kJ/m2 UVB radiation. To assess the effect of the carbohydrates on keratinocytes, murine Pam212 cells were exposed to 300 J/m2 UVB radiation and treated for 1 h with tamarind xyloglucans or Aloe poly/oligosaccharides. Treatment of keratinocytes with immunoprotective carbohydrates reduced IL‐10 production by approximately 50% compared with the cells treated with UV radiation alone and completely blocked suppressive activity of the culture supernatants in vivo. The tamarind xyloglucans also blocked UV‐activated phosphorylation of SAPK/JNK protein but had no effect on p38 phosphorylation. These results indicate that animals, like plants, may use carbohydrates to regulate responses to environmental stimuli.
Polyphenolic Antioxidant (‐)‐Epigallocatechin‐3‐Gallate from Green Tea Reduces UVB‐lnduced Inflammatory Responses and Infiltration of Leukocytes in Human Skin
Authors: Katiyar Santosh K. , Matsui Mary S. , Elmets Craig A. , Mukhtar Hasan
Published: January 2008

Abstract— Identification of natural products capable of affording protection against UVB radiation‐induced inflammatory responses and generation of oxidative stress may have important human health implications. The UVB exposure‐induced skin injury and oxidative stress has been associated with a variety of skin disease conditions including photoaging, inflammation and cancer. Tea is a popular beverage consumed worldwide. In several mouse skin models, topical application as well as oral consumption of green tea has been shown to afford protection against chemical and UVB‐induced carcinogenesis and inflammatory responses. In the present study, we investigated in human skin, whether topical application of (‐)epigallocatechin‐3‐gallate (EGCG), the major polyphenolic constituent in green tea, inhibits UVB‐induced infiltration of leukocytes (macrophage/neutrophils), a potential source of generation of reactive oxygen species (ROS), and generation of prostaglandin (PG) metabolites. Human subjects were UVB irradiated on sun‐protected skin to four times their minimal erythema dosage (MED) and skin biopsies or keratomes were obtained either 24 h or 48 h later. We found that topical application of EGCG (3 mg/2.5 cm2) before UVB (4 MED) exposure to human skin significantly blocked UVB‐induced infiltration of leukocytes and reduced myeloperoxidase activity. These infiltrating leukocytes are considered to be the major source of generation of ROS. In the same set of experiments we found that topical application of EGCG before UVB exposure decreased UVB‐induced erythema. In additional experiments, we found that microsomes from EGCG pretreated human skin and exposed to UVB, compared to UVB exposure alone, produced significantly reduced PG metabolites, particularly PGE2. The PG metabolites play a critical role in free radical generation and skin tumor promotion in multistage skin carcinogenesis. Careful microscopic examination of skin sections, stained with hematoxylin and eosin, under higher magnification (x400) also revealed that EGCG pretreated and UVB exposed human skin contained fewer dead cells in the epidermis with comparison to nonpretreated UVB‐exposed skin. Taken together, our data demonstrate that EGCG has the potential to block the UVB‐induced infiltration of leukocytes and the subsequent generation of ROS in human skin. This may explain the possible mechanism involved in anti‐inflammatory effects of green tea. We suggest that EGCG may be useful as a topical agent for protection against UVB‐induced ROS‐associated inflammatory dermatoses, photoaging and photocarcinogenesis. Further studies are warranted in this direction.
Phototoxic Effects of Hypericum Extract in Cultures of Human Keratinocytes Compared with Those of Psoralen
Authors: Bernd A. , Simon S. , Bosca A. Ramirez , Kippenberger S. , Alperi J. Diaz , Miquel J. , Garcia J. F. Villalba , Mira D. Pamies , Kaufmann R.
Published: January 2008

Abstract— Extracts of Hypericum perforatum (St. John's wort) are used in the treatment of depression. They contain the plant pigment hypericin and hypericin derivates. These compounds have light‐dependent activities. In order to estimate the potential risk of phototoxic skin damage during antidepressive therapy, we investigated the phototoxic activity of hypericin extract using cultures of human keratinocytes and compared it with the effect of the well‐known phototoxic agent psoralen. The absorbance spectrum of our Hypericum extract revealed maxima in the whole UV range and in parts of the visible range. We cultivated human keratinocytes in the presence of different Hypericum concentrations and irradiated the cells with 150 mJ/cm2 UVB, 1 J/cm2 UVA or 3 h with a white light of photon flux density 2.6 μmol m 2 s−1. The determination of the bromodeoxyuridine incorporation rate showed a concentration—and light‐dependent decrease in DNA synthesis with high hypericin concentrations (≥50 μg/mL) combined with UVA or visible light radiation. In the case of UVB irradiation a clear phototoxic cell reaction was not detected. We found phototoxic effects even with 10 ng/mL psoralen using UVA with the same study design as in the case of the Hypericum extract. These results confirm the phototoxic activity of Hypericum extract on human keratinocytes. However, the blood levels that are to be expected during antidepressive therapy are presumably too low to induce phototoxic skin reactions.
Identification and Partial Characterization of an Unusual Distribution of the Photosensitizer meta‐Tetrahydroxyphenyl Chlorin (Temoporfin) in Human Plasma
Authors: Hopkinson Hazel J. , Vernon David I. , Brown Stanley B.
Published: January 2008

Abstract— Temoporfin (m‐THPC) is an extremely powerful photosensitizing drug, more than 100‐fold more photocytotoxic than Photofrin and many other drugs. The reasons for this are not yet known but are likely to be associated with the mechanism of uptake of the drug and its intratumoral and intracellular localization. Uptake itself is likely to be dependent upon the plasma binding of the drug following administration. In the current work, we have shown that the addition of m‐THPC to human plasma in vitro at clinically relevant doses of sensitizer and administration solvent (diluant) gives rise to a protein‐binding pattern quite different to that of Photofrin and other hydrophobic drugs as judged by density‐gradient ultra centrifugation. Analysis of the binding immediately after addition to human plasma has shown that lipoprotein binding accounts for only a minor proportion of the sensitizer, which is mainly associated with a high‐density protein fraction that is not coincident with serum albumin. The m‐THPC protein complex does not fluoresce significantly even on dilution. This binding pattern is highly dependent on administration conditions and storage. Over a period of 6–8 h at 37°C the m‐THPC that is associated with this unidentified fraction redistributes to the plasma lipoproteins. Plasma collected from rats after intravenous administration of m‐THPC also contains this low fluorescent complex, showing that this phenomenon is not limited to human plasma and also occurs in vivo. It is postulated that the m‐THPC bound to the unknown protein fraction is highly aggregated and that it is likely to be taken up into tissues in this form. This unusual uptake may possibly be associated with the very high activity of m‐THPC and also to the recent finding of a second peak in the plasma pharmacokinetics of the drug.
Photophysical Properties of the Cationic Form of Neutral Red
Authors: Singh M. K. , Pal H. , Bhasikuttan A. C. , Sapre A. V.
Published: January 2008

Abstract— Photophysical properties of the cationic form of neutral red (NRH+), a phenazine‐based dye of biological importance, have been investigated in several protic and aprotic solvents using optical absorption, steady‐state and time‐resolved fluorescence and picosecond laser flash photolysis techniques. Absorption and fluorescence characteristics of the dye in protic solvents indicate the existence of intermolecular hydrogen bonding between the NRH+ and solvent molecules in the ground state as well as in the excited state. Measurements of the fluorescence lifetime in normal and heavy water also support the formation of intermolecular hydrogen bonding. Time‐resolved transient absorption spectra obtained in the picosecond laser flash photolysis experiments show only the absorption band due to the Sn← S1 absorption. The picosecond transient absorption results do not indicate any spectral shifts attributable to the hydrogen bond formation dynamics between the excited NRH+ and the protic solvent molecules. It is inferred that the hydrogen bonding dynamics are much faster than the time resolution of our picosecond setup (∼35 ps).
Role of the Immune System in Mediating the Antitumor Effect of Benzophenothiazine Photodynamic Therapy
Authors: Hendrzak‐Henion Jill A. , Knisely Terrence L. , Cincotta Louis , Cincotta Eric , Cincotta Anthony H.
Published: January 2008

Abstract— The role of the host immune system in contributing to tumor regression following benzophenothiazine photodynamic therapy (PDT) was examined. Photodynamic therapy with 2‐iodo‐5‐ethylamino‐9‐diethylaminobenzo[a]‐phenothiazinium chloride (2I‐EtNBS) eradicated EMT‐6 mammary fibrosarcomas in 75–100% of treated mice. In contrast, PDT failed to inhibit tumor growth in T‐cell‐deficient nude mice. Furthermore, T‐cell depletion studies with anti‐CD8 antibody revealed that the CD8+ T‐cell population was critical for an effective PDT response (tumor volume 14 days post‐PDT: 262 mm3vs 59 mm3 in controls; P < 0.01). Because anti‐CD4 antibody inhibited tumor growth in the absence of PDT, the role of CD4+ T cells remains unclear. Depletion of natural killer (NK) cells in vivo with anti‐asialo‐GM1 antibody significantly reduced a suboptimal PDT effect relative to vehicle controls (tumor volume 13 days post‐PDT: 513 mm3vs 85 mm3 respectively; P < 0.001). However, splenic NK cells obtained from PDT‐treated tumor‐bearing mice were not cytotoxic in vitro against EMT‐6 cells, suggesting that NK cells contribute to the PDT effect in vivo by an indirect mechanism. In addition, when mice with complete tumor regression following PDT were rechallenged 28 days later with 5 × 105 EMT‐6 cells, tumor growth was signficantly inhibited as compared to controls (tumor volume 40 days postrechallenge: 137 mm3vs 833 mm3 in controls; P < 0.03; percent animals without tumor in five experiments: 67%vs 8% in controls). Collectively, these results demonstrate that CD8+ T cells are required to prevent tumor regrowth after 2I‐EtNBSPDT, NK cells contribute to this response and such PDT can elicit protective antitumor immunity.
Near‐infrared Fluorescence Spectroscopy Detects Alzheimer's Disease In Vitro
Authors: Hanlon Eugene B. , Itzkan Irving , Dasari Ramachandra R. , Feld Michael S. , Ferrante Robert J. , McKee Ann C. , Lathi Devayani , Kowall Neil W.
Published: January 2008

Abstract. The purpose of this study was to investigate whether near‐infrared (NIR) fluorescence spectroscopy could be used to detect Alzheimer's disease (AD) by brain tissue autofluorescence. Unfixed temporal cortex specimens from AD cases and age‐matched, non‐AD controls were frozen at autopsy and then thawed just prior to spectral measurement. Spectra of intrinsic tissue fluorescence induced by 647 nm light were recorded from 650 to 850 run. We used principal component analysis of the tissue spectra from 17 AD cases and 5 non‐AD control cases in a calibration study to establish a diagnostic algorithm. Retrospectively applied to the calibration set, the algorithm correctly classified 23 of 24 specimens. In a prospective study of 19 specimens from 5 AD brains and 2 non‐AD control brains, 3 of the 4 control specimens and all AD specimens were correctly diagnosed. Both the excitation light used and the measured brain tissue autofluorescence are at NIR wavelengths that can propagate through skull and overlying tissue. Therefore, our results demonstrate an optical spectroscopic technique that carries direct molecular level information about disease. This is the first step toward a clinical tool that has the potential to be applied to the noninvasive diagnosis of AD in living patients.
Light‐induced Damage in the Retina: Differential Effects of Dimethylthiourea on Photoreceptor Survival, Apoptosis and DNA Oxidation
Authors: Organisciak Daniel T. , Darrow Robert A. , Barsalou Linda , Darrow Ruth M. , Lininger Linda A.
Published: January 2008

Abstract. In the rat, photoreceptor cell death from exposure to intense visible light can be prevented by prior treatment with antioxidants. In this study we subjected albino rats raised in dim cyclic light and rats made more susceptible to light damage by rearing in darkness to exposures of green light that led to similar losses of photoreceptor cells. Rhodopsin and photoreceptor DNA, indicators of the number of surviving photoreceptor cells, were determined at various times over a period of 14 days after light exposure. Fragmentation of DNA was determined over a similar time course by neutral and alkaline agarose gel electrophoresis. Apoptosis in retinal DNA was measured by quantitating the appearance of 180 base pair (bp) nucleosomal fragments. Oxidation of DNA was measured by electrochemical detection of the nucleoside 8‐hydroxydeoxyguanosine (8‐OHdG) after separation by high‐performance chromatography. For albino rats reared in dim cyclic light, 24 h of intense light exposure resulted in the loss of 50% rhodopsin and photoreceptor cell DNA. In dark‐reared rats, the losses were 40%, respectively, after only 3 h of intense light treatment. In both cases pretreatment with the antioxidant dimethylthiourea (DMTU) prevented rhodopsin and photoreceptor cell DNA loss. The kinetics of the light‐induced apoptosis depended markedly on the rearing environment of the rats. The DNA ladders appeared within 12 h of the onset of intense light in the rats reared in dim cyclic light. In these rats the 180 bp fragment was at two‐thirds of its maximum intensity immediately after 24 h of light exposure and reached the maximum 12 h later. Dimethylthiourea partially inhibited ladder formation in rats reared in dim cyclic light and delayed the time of appearance of the 180 bp maximum by 6 h. By contrast, in rats reared in darkness the 180 bp fragment was undetected immediately after 3 h of light exposure and
Photogeneration of Hydrated Electrons, Nitrogen‐Centered Radicals and Singlet Oxygen from Naphazoline: A Laser Flash Photolysis Study
Authors: Sortino S. , Scaiano J. C.
Published: January 2008

The transient intermediates involved in the photochemistry of naphazoline (NP, 2‐[1‐naphthylme‐thyl]imidazoline) have been examined using laser flash photolysis techniques. The photoreactivity of the drug is characterized by a photoionization process occurring through a mixture of mono‐ and biphotonic pathways. An intramolecular electron transfer involving both the imidazoline and the naphthalene moieties leads to the formation of nitrogen‐centered radicals. The generation of singlet oxygen from the lowest excited triplet state of NP is also observed. The results obtained demonstrate the potential for NP to act as a both a type I and type II photosensitizer.
The Temperature Dependence of Protoporphyrin IX Production in Cells and Tissues
Authors: Moan Johan , Berg Kristian , Gadmar Øystein B. , Iani Vladimir , Ma LiWei , Juzenas Petras
Published: January 2008

The formation of protoporphyrin IX (PpIX) in human skin during topical application of 5‐aminolevulinic acid (ALA) was found to be strongly temperature dependent, with an activation energy of about 17 kcal/mol. This temperature dependence is mainly related to porphyrin production and not to ALA penetration into the skin. The penetration of ALA into mouse and human skin was almost temperature independent. The activation energy of PpIX production in mouse skin was practically identical with that in human skin. The activation energy of ALA uptake by cells in vitro was about 10 kcal/mol and that for PpIX production was about 13 kcal/mol. The latter activation energy was within the error limits similar to that for the activity of the enzyme porphobilinogen deaminase, suggesting that this enzyme might represent a rate‐limiting step for PpIX production in living tissue.
Color Tuning Mechanism of Human Red and Green Visual Pigments
Authors: Kakitani Toshiaki , Beppu Yoshitaka , Yamada Atsushi
Published: January 2008

We investigated the molecular mechanism of a rather large red shift of 31 nm in a human red pigment compared with a human green pigment. In this analysis, we paid special attention to the phenomenon of nonadditivity of spectral shifts due to substitution of the key amino acids (OH‐bearing amino acids) and the phenomenon of cooperativity by which the spectral shifts due to substitution of the key amino acids in the protein environment of red pigment are about 1.5 times larger than that in the protein environment of green pigment. The analysis was made by using a model of three active sites on which the key amino acids are located and four effective sites by which the effect of the key amino acids is modified. As a result, we found that the interaction between the active sites that occurs through the repolarization of the chromophore induced by the key amino acid is essential for the nonadditivity phenomenon. We also found that the interaction between the active site and the effective site plays a major role in the cooperativity phenomenon. More directly, we say that the highly polarizable property of the chromophore is the origin of the rather large red shift in red pigment. Based on these analyses, we conclude that the interaction between the polarizable chromophore and the protein moiety has the capability of producing a significant spectral shift, at least 1000 cm1, even by substitution of moderate polar residues of the OH‐bearing amino acids.
Development of hyperinsulinemia and insulin resistance during the early stage of weight gain
Authors: Erdmann Johannes , Kallabis Bianca , Oppel Ulrich , Sypchenko Oleg , Wagenpfeil Stefan , Schusdziarra Volker
Published: January 2008

Obesity is associated with insulin resistance and hyperinsulinemia, which is considered to be a core component in the pathophysiology of obesity-related comorbidities. As yet it is unknown whether insulin resistance and hyperinsulinemia already develop during weight gain within the normal range. In 10 healthy male subjects the effect of intentional weight gain by 2 BMI points was examined on insulin. C-peptide and glucose levels following a meal, 75 g of glucose, and a two-step hyperglycemic clamp increased plasma glucose by 1.38 and 2.75 mmol/l, respectively. Baseline insulin, C-peptide, and glucose concentrations were significantly higher after weight gain from 21.8 to 23.8 kg/m2 BMI within 41/2 mo. Calculations of insulin secretion and clearance indicate that reduced insulin clearance contributes more to post-weight gain basal hyperinsulinemia than insulin secretion. Following oral or intravenous stimulation insulin concentrations were significantly higher post-weight gain during all three test conditions, whereas C-peptide and glucose levels did not differ. Calculations of insulin secretion and clearance demonstrated that higher stimulated insulin concentrations are entirely due to clearance but not secretion. Despite significantly higher insulin levels, the rate of intravenous glucose required to maintain the defined elevation of glucose levels was either identical (1.38 mmol/l) or even significantly lower (2.75 mmol/l) following weight gain. The present study demonstrates for the first time that insulin resistance already develops during weight gain within the normal range of body weight. The associated basal and stimulated hyperinsulinemia is the result of differentiated changes of insulin secretion and clearance, respectively.
Two-Photon Excitation of Potentiometric Probes Enables Optical Recording of Action Potentials From Mammalian Nerve Terminals In Situ
Authors: Fisher Jonathan A. N. , Barchi Jonathan R. , Welle Cristin G. , Kim Gi-Ho , Kosterin Paul , Obaid Ana Lía , Yodh Arjun G. , Contreras Diego , Salzberg Brian M.
Published: January 2008

We report the first optical recordings of action potentials, in single trials, from one or a few (∼1–2 μm) mammalian nerve terminals in an intact in vitro preparation, the mouse neurohypophysis. The measurements used two-photon excitation along the “blue” edge of the two-photon absorption spectrum of di-3-ANEPPDHQ (a fluorescent voltage-sensitive naphthyl styryl-pyridinium dye), and epifluorescence detection, a configuration that is critical for noninvasive recording of electrical activity from intact brains. Single-trial recordings of action potentials exhibited signal-to-noise ratios of ∼5:1 and fractional fluorescence changes of up to ∼10%. This method, by virtue of its optical sectioning capability, deep tissue penetration, and efficient epifluorescence detection, offers clear advantages over linear, as well as other nonlinear optical techniques used to monitor voltage changes in localized neuronal regions, and provides an alternative to invasive electrode arrays for studying neuronal systems in vivo.