bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensity‐Dependent Enzyme Photosensitization Using 532 nm Nanosecond Laser Pulses
Authors: Lambert C. R. , Stiel H. , Leupold D. , Lynch M. C. , Kochevar I. E.
Published: January 2008

Abstract— The intensity dependence of the rose bengal (RB)‐photosensitized inhibition of red blood cell acetylcholinesterase has been studied experimentally and the results compared to a quantitative excitation/deactivation model of RB photochemistry. Red blood cell membrane suspensions containing 5 μM RB were irradiated with 532 nm, 8 ns laser pulses with energies between 1 and 98.5 mJ. A constant dose (7 J) was delivered to all samples by varying the total number of pulses. At incident energies greater than ∼ 4.5 mJ/pulse, the efficiency for photosensitized enzyme inhibition decreased as the energy/pulse increased. The generation of RB triplet state was monitored as a function of laser energy and the triplet‐triplet absorption coefficient was determined to be 1.9 × 104M−1 cm−1 at 530 nm. The number of singlet oxygen molecules produced at each intensity was calculated from both the physico‐mathematical model and from laser flash photolysis results. The results indicated that the photosensitized inhibition of acetylcholinesterase was exclusively mediated by singlet oxygen, even at the highest laser intensities employed.
Role of Enterobactin and Intracellular Iron in Cell Lethality During Near‐UV Irradiation inEscherichia coli
Authors: Hoerter J. , Pierce A. , Troupe C. , Epperson J. , Eisenstark A.
Published: January 2008

Abstract—InEscherichia coli, furmutants that constitutively express their native iron chelating agent, enterobactin, are significantly more sensitive to near‐UV radiation (NUV) than wild type. AnentAmutant, which is incapable of synthesizing enterobactin, is equal to wild type in resistance to NUV irradiation. However, the addition of Fe+3enterobactin but not Al+1enterobactin toentAcell suspensions just prior to irradiation results in an increased sensitivity to NUV irradiation. Afesmutant, which is unable to reduce and release iron from enterobactin, is significantly more sensitive to NUV irradiation than wild type. The addition of nontoxic levels of H2O2(5 μM) just prior to irradiation significantly increases sensitivity of bothfurandfesmutants. These results suggest that one mechanism by which NUV irradiation leads to cell lethality is by creating a transient iron overload, producing very favorable conditions for the production of highly deleterious free radicals through a variety of mechanisms that lead to oxidative stress and DNA damage including lethal and mutagenic lesions. These results are consistent with the hypothesis that enterobactin is an endogenous chromophore for NUV and contributes to cell lethalityviathe destruction of its ligand, releasing Fe+2into the cytoplasm to catalyze the production of highly reactive hydroxyl radicals and other toxic oxygen speciesviathe Haber‐Weiss reaction.
Two‐Color Two‐Photon Excitation of Fluorescence
Authors: Lakowicz Joseph R. , Gryczynski Ignacy , Malak Henryk , Gryczynski Zygmunt
Published: January 2008

Abstract— We report the observation of two‐photon excitation of an organic fluorophore with two different wavelengths, a phenomenon we refer to as two‐color two‐photon (2C2P) excitation. Ultraviolet emission of p‐Merphenyl at 340 nm was observed when the sample was illuminated with both 375 and 750 nm pulses from a picosecond dye laser. The emission of p‐terphenyl was about 100‐fold and more than 1000‐fold less for illumination at only 375 or 750 nm, respectively. Observation of the 2C2P signal required temporal and spatial overlap of the 375 and 750 nm pulses. The amplitude of the signal depended on the polarization of each beam. 2C2P excitation can have applications in fluorescence microscopy and elsewhere when spatially localized excitation is desirable.
Cervical Precancer Detection Using a Multivariate Statistical Algorithm Based on Laser‐Induced Fluorescence Spectra at Multiple Excitation Wavelengths
Authors: Ramanujam Nirmala , Mitchell Michele Follen , Mahadevan‐Jansen Anita , Thomson Sharon L. , Staerkel Gregg , Malpica Anais , Wright Thomas , Atkinson Neely , Richards‐Kortum Rebecca
Published: January 2008

Abstract— A portable fluorimeter was developed and utilized to acquire fluorescence spectra from 381 cervical sites in 95 patients at 337, 380 and 460 nm excitation immediately prior to colposcopy. A multivariate statistical algorithm was used to extract clinically useful information from tissue spectra acquired in vivo. Two full‐parameter algorithms were developed using tissue fluorescence emission spectra at all three excitation wavelengths (161 excitation‐emission wavelength pairs) for cervical precancer (squamous intraepithelial lesion [SIL]) detection: a screening algorithm that discriminates between SIL and non‐SIL with a sensitivity of 82 ± 1.4% and specificity of 68 ± 0.0%, and a diagnostic algorithm that differentiates high‐grade SIL from non‐high‐grade SIL with a sensitivity and specificity of 79 ± 2% and 78 ± 6%, respectively. Multivariate statistical analysis was also employed to reduce the number of fluorescence excitation‐emission wavelength pairs needed to redevelop algorithms that demonstrate a minimum decrease in classification accuracy. Two reduced‐parameter algorithms that employ fluorescence intensities at only 15 excitation‐emission wavelength pairs were developed: the screening algorithm differentiates SIL from non‐SIL with a sensitivity of 84 ± 1.5% and specificity of 65 ± 2% and the diagnostic algorithm discriminates high‐grade SIL from non‐high‐grade SIL with a sensitivity and specificity of 78 ± 0.7% and 74 ± 2%, respectively. Both the full‐parameter and reduced‐parameter screening algorithms discriminate between SIL and non‐SIL with a similar specificity (±5%) and a substantially improved sensitivity relative to Pap smear screening. A comparison of the full‐parameter and reduced‐parameter diagnostic algorithms to colposcopy in expert hands indicates that all three have a very similar sensitivity and specificity for differentiating high‐grade SIL from non‐high‐grade SIL.
Blue‐Light Receptor Requirement for Gravitropism, Autochemotropism and Ethylene Response in Phycomyces*
Authors: Campuzano Victoria , Galland Paul , Alvarez Maria I. , Eslava Arturo P.
Published: January 2008

Light, gravity and ethylene represent for plants and fungi important environmental cues for spatial orientation and growth regulation. Coordination of the frequently conflicting stimuli requires signal‐integration sites, which, however, remain largely unidentified. The genetic and physiological basis for signal integration was investigated with a set of phototropism mutants (genotype mad) of the UV‐ and blue‐light‐sensitive fungus Phycomyces blakes‐leeanus, which responds also to gravity, ethylene and nearby obstacles (autochemotropism or avoidance response). Both, class 1 and class 2 mutants display a reduced sensitivity to visible light. Class 1 mutants with defects in genes mad A, B, C, Z have preserved their sensitivity to gravity and ethylene, whereas class 2 mutants with defects in genes mad D, E, F, G, J have lost it. We found that the phototropic sensitivity of class 1 mutants is affected roughly to the same extent in far UV and blue light. In contrast, the sensitivity loss of class 2 mutants is restricted mainly to the near‐UV and the blue‐light region, whereas the sensitivity to far UV is only mildly affected. This behavior of the class 2 mutants indicates that different photoreceptors mediate phototropism in far‐UV and in near‐UVhlue light. The photogravitropic action spectra for two class 2 mutants with defects in genes mad F and mad J display distortions between 342 and 530 nm and a bathochromic shift relative to the action spectrum of the wild type. These features indicate that the mad F and mad J mutants are affected at the level of the blue‐light photoreceptor system. As an implication we infer that an intact near‐UVhlue‐light photoreceptor system is required even in darkness for negative gravitropism, the ethylene response and autochemotropism. In Phycomyces, signal integration occurs, at least in part, at the level of the near‐U Vhlue‐light photoreceptor system.
The Effects of Methylene Blue and Oxygen Concentration on the Photoinactivation of Qβ Bacteriophage
Authors: Lee Denis , Foux Michael , Leonard Edward F.
Published: January 2008

Abstract— Concentration effects of methylene blue (MB) and oxygen on the photoinactivation rate of Qβ bacteriophage were examined. The effect of initial virus concentration was verified on the similar f2 phage. The inactivation rate, k, is an increasing function of MB and O2 concentration and shows saturation with respect to MB concentration. Thus the results suggest that MB must adsorb to Qβ sites and oxygen must be present for photoinactivation to occur. The inactivation rate is independent of the initial number of phage particles present before inactivation, indicating that inactivation does not depend upon interaction among viral particles or on surface effects. The results indicate that at least two different viral phenotypes exist within the wild‐type Qβ and f2 populations: one susceptible and the other resistant.
Induction of Proinflammatory Cytokines in Human Epidermoid Carcinoma Cells by in vitro Ultraviolet A1 Irradiation
Authors: Morita Akimichi , Grewe Markus , Grether‐Beck Susanne , Olaizola‐Horn Sylvia , Krutmann Jean
Published: January 2008

Abstract— Ultraviolet radiation‐induced expression of cytokines by keratinocytes is important for the pathogenesis of polymorphous light eruption (PLE). Because UVA1 radiation rather than UVB radiation might be a more important trigger for PLE, cells from the human epidermoid carcinoma cell line KB were exposed in vitro to UVA1 radiation (30 J/cm2) and subsequently analyzed for cytokine expression. Ultraviolet A1 irradiation induced tumor necrosis factor (TNF)‐a and interleukin (IL)‐8 expression in KB cells at the mRNA and protein level. Upregulation of cytokine mRNA levels followed a Diphasic pattern. This effect was specific for TNFa and IL‐8 because UVA1 radiation did not induce expression of IL‐la or IL‐6 in these cells. Ultraviolet Al radiation‐induced expression of intercellular adhesion molecule‐1 in KB cells previously was found to depend on the thiol status of these cells. Therefore, KB cells were treated with DL‐buthionine‐[S, R]‐sulfoximine (BSO), a specific inhibitor of de novo glutathione synthesis. Exposure of BSO‐pretreated KB cells to UVA1 radiation significantly induced IL‐1α and IL‐6 mRNA and protein expression. These studies demonstrate the capacity of UVA1 radiation to induce cytokine expression in human epidermoid carcinoma cells. This immunomodulatory effect may be mediated by thiol‐status‐dependent and ‐independent mechanisms.
Photodynamic Therapy of 9L Gliosarcoma with Liposome‐Delivered Photofrin
Authors: Jiang Feng , Lilge Lothar , Logie Bradley , Li Yi , Chopp Michael
Published: January 2008

Abstract— The effect of Photofrin encapsulated in a liposome delivery vehicle for photodynamic therapy (PDT) of the 9L gliosarcoma and normal rat brain was tested. We hypothesized that the liposome vehicle enhances therapeutic efficacy, possibly by increasing tumor tissue concentration of Photofrin. Male Fisher rats bearing a 9L gliosarcoma were treated 16 days after intracerebral tumor implantation with either Photofrin in dextrose (n = 5) or Photofrin in liposome (n = 6). Nontumor‐bearing animals were treated with Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle. Tissue concentrations of Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle were measured in tumor, brain adjacent to tumor and in normal brain tissue. Photofrin was administered (intraperitoneally) at a dose of 12.5 mg/kg and PDT (17 J/cm2 of 632 nm light at 100 mW/cm2) was performed 24 h after Photofrin administration. Brains were removed 24 h after PDT and stained with hematoxylin and eosin for analysis of cellular damage. The PDT using Photofrin in the liposome vehicle caused significantly more damage to the tumor (P < 0.001) than did PDT with Photofrin in dextrose. The PDT of tumor with Photofrin delivered in liposomes caused a 22% volume of cellular necrosis, while PDT of tumor with Photofrin delivered in dextrose caused only scattered cellular damage. Photofrin concentration in tumors was significantly higher (P= 0.021) using liposome (33.8 ± 18.9 μg/g) compared to dextrose delivery (5.5 ± 1.5 μg/g). Normal brain was affected similarly in both groups, with only scattered cellular necrosis. Our data suggest that the liposome vehicle enhances the therapeutic efficacy of PDT treatment of 9L tumors.
Preclinical Assessment of Hypocrellin B and Hypocrellin B Derivatives as Sensitizers for Photodynamic Therapy of Cancer: Progress Update
Authors: Miller Gerald G. , Brown Kevin , Ballangrud Åse M. , Barajas Oscar , Xiao Z. , Tulip John , Lown J. William , Leithoff Jacqueline M. , Allalunis‐Turner M. Joan , Mehta Ram D. , Moore Ronald B.
Published: January 2008

Abstract— Hypocrellins are perylenequinone pigments with substantial absorption in the red spectral region and high singlet oxygen yield. They are available in pure monomelic form and may be derivatized to optimize properties of red light absorption, tissue biodistribution and toxicity. In vitro screening of synthetic derivatives of the naturally occurring compound, hypocrellin B (HB), for optimal properties of cyto‐(dark) toxicity and phototoxicity resulted in selection of three compounds for preclinical evaluation: HBEA‐R1 (ethanolaminated HB), HBBA‐R2 (butylaminated HB) and HBDP‐R1 [2‐(N,N‐dimethylami‐no)‐propylamine‐HB]. Extinction coefficients at 630 nm (φ630) are 6230, 6190 and 4800, respectively; and 1O2 quantum yields, φ, 0.60, 0.32 and 0.42. Intracellular uptake is essentially complete within 2 h (HBEA‐R1, HBBA‐R2) and 20 h (HBDP‐R1). Greatest uptake is associated with lysosomes and Golgi. The HBEA‐R1 and HBBA‐R2 elicit phototoxicity in vitro primarily via the type II mechanism, with some type I activity under stringently hypoxic conditions. Transcutaneous phototherapy with HBEA‐R1 permanently ablates EMToVEd tumors growing in the flanks of Balb/c mice, with minimal cutaneous effects. The HBBA‐R2 does not elicit mutagenic activity in strains TA98 and TA100 of Salmonella typhi‐murium. Further development of selected hypocrellin derivatives as photosensitizers for photodynamic therapy is warranted.
Excited State Properties of the Siderophore Pyochelin and its Complex with Zinc Ions
Authors: Namiranian Sholeh , Richardson David J. , Russell David A. , Sodeau John R.
Published: January 2008

Abstract— The critical effects of pH on the electronic absorption and fluorescence characteristics of the siderophore, pyochelin, are investigated. A single anionic species is shown to be sufficient to explain the data obtained under alkaline conditions. In acidic solutions, several competing ground‐ and excited‐state equilibria are present, which lead to fluorescence emissions from both the protonated form of pyochelin and its phenolate ion. From the spectroscopic data we are also able to show that pyochelin interacts with zinc ions in the ground state via its anionic form, thereby confirming that this siderophore does not bind Fe(III) ions uniquely.
UVB Irradiation Induces Changes in Cellular Localization and Phosphorylation of Mouse HSP27
Authors: Nozaki Junichi , Takehana Makoto , Kobayashi Shizuko
Published: January 2008

Abstract— We investigated the induction, cellular localization and phosphorylation of a low‐molecular weight stress protein (heat shock protein 27, HSP27) by UVB (290‐320 nm, max. 312 nm) irradiation stress using immunoblot and indirect immunofluorescence analysis in in vivo and in vitro experiments. The HSP27 was constitutively expressed and distributed in the cytoplasmic fraction of Pam 212 cells (mouse keratinocyte line) or dorsal skin. The increase in the cytoplasm HSP27 level induced by UVB irradiation was less than two‐fold that in nonirra‐diated controls. On the other hand, the translocation of HSP27 from cytoplasm to the nucleus or perinuclear area was time‐ and dose‐dependently induced by UVB irradiation. After UVB irradiation, three isoforms having different isoelectric points were detected in nucleic HSP27 by two‐dimensional immunoblotting. The most basic isoform was the unphosphorylated type and the two acidic isoforms were phosphorylated, suggesting that HSP27 is phosphorylated in response to UVB irradiation and accumulates in or around the nucleus as a phosphorylated isoform. These results suggest that the translocation and phosphorylation of HSP27 are induced in response to UVB‐irradiation stress.
Phthalocyanine Photodynamic Therapy: Disparate Effects of Pharmacologic Inhibitors on Cutaneous Photosensitivity and on Tumor Regression
Authors: Anderson Cathy , Hrabovsky Sharon , McKinley Yvonne , Tubesing Karen , Tang Hai‐Ping , Dunbar Robert , Mukhtar Hasan , Elmets Craig A.
Published: January 2008

Abstract— The phthalocyanines are promising second‐generation photosensitizers that are being evaluated for the photodynamic therapy (PDT) of malignant tumors. In vivo studies with the silicon phthalocyanine Pc 4 have shown that it is highly effective at causing regression of RIF‐1 tumors in C3H/HeN mice in PDT protocols. Because cutaneous photosensitivity is the major complication of photosensitizers used for PDT, experiments were performed to evaluate the effect of inhibitors of the inflammatory response (cyproheptadine, dexamethasone, pentoxifylline, and tumor necrosis factor alpha [TNF‐α] antibodies) on Pc 4‐induced cutaneous photosensitivity and tumor regression. The C3H/HeN mice were injected with either Pc 4 or Photofrin and were exposed to 86 J/cm2of filtered radiation emitted from a solar simulator. Animals were irradiated at 1, 3, 7, 10, 14 and 28 days post‐injection. Cutaneous photosensitivity was assessed using the murine ear‐swelling response. Cyproheptadine, dexamethasone, pentoxifylline and TNF‐α antibodies were administered prior to illumination to assess their ability to block Pc 4‐induced cutaneous photosensitivity and to evaluate whether such treatment adversely influenced Pc 4 PDT‐induced tumor regression. Compared to Photofrin, Pc 4 produced cutaneous photosensitivity that was transient, resolving within 24 h, and that could be elicited for only 10 days after administration. In contrast, Photofrin caused photosensitivity that required 4 days to resolve and could be elicited for at least 1 month after it was administered. The Pc 4‐induced cutaneous photosensitivity could be blocked by corticosteroids and an inhibitor of vasoactive amines (cyproheptadine). The TNF‐a gene transcription was found to increase in keratinocytes following treatment with Pc 4 and light. The anti‐TNF‐a antibodies and pentoxifylline, an inhibitor of cytokine transcription, also prevented cutaneous photosensitivity, implicating TNF‐α in the pathogenesis of Pc 4‐induced cutaneous photosensitivity. None of these agents had any effect on Pc 4 PDT‐induced tumor regression. Cyproheptadine, dexamethasone, pentoxifylline and TNF‐a antibodies may be valuable pharmacologic agents in the management of cutaneous photosensitivity associated with PDT without altering the efficacy of this new therapeutic modality. The findings suggest that it should be possible to devise PDT protocols that block cutaneous photosensitivity without impairing the anti‐tumor response to the agents.
Meso‐Tetraphenylporphyrin Dimer Derivative as a Potential Photosensitizer in Photodynamic Therapy
Authors: Faustino Maria A. F. , Neves Maria G. P. M. S. , Vicente Maria G. H. , Cavaleiro Jose A. S. , Neumann Marcus , Brauer Hans‐D. , Jori Giulio
Published: January 2008

Abstract— Studies on the synthesis, preliminary in vivo biological activity, singlet oxygen and fluorescence yields of a di‐meric porphyrin (Dl) are described. The pharmacokinetic behavior and photodynamic properties of the dimer Dl were examined in Balb/c mice bearing an MS‐2 fibrosarcoma. Compound Dl shows a high selectivity for tumor localization (tumor/peritumoral tissue ratios of dye concentration ranging between ca 100 and 140 at 24 h after drug administration of 5.0‐1.0 mg kg‐1 into DL‐AL‐dipalmitoylphosphatidylcholine liposomes). The photo‐therapeutic efficiency of dimer Dl was evaluated by following the growth curves of fibrosarcoma irradiated with red light (600‐700 nm) with a total dose of 400 J cm‐2, at 24 h after intravenous injection. Photodynamic therapy‐treated tumors showed a significant delay in growth as compared to untreated control mice. The results obtained suggest that the porphyrin dimer Dl may be a promising candidate for further use in PDT experiments.
Fundamental Differences of Excitation Spectrum between Malignant and Benign Breast Tissues
Authors: Yang Yuanlong , Katz A. , Celmer Edward J. , Zurawska‐Szczepaniak Margaret , Alfano R. R.
Published: January 2008

Abstract— Differences observed in the UV excitation spectrum of malignant and benign breast tissues are used to distinguish between malignant and benign breast tissues. These changes are attributed to changes with specialized proteins.
Human Blue‐light Photoreceptor hCRY2 Specifically Interacts with Protein Serine/Threonine Phosphatase 5 and Modulates Its Activity
Authors: Zhao Shaying , Sancar Aziz
Published: January 2008

Abstract— Photolyase/blue‐light photoreceptor family of proteins includes cyclobutane pyrimidine dimer photolyase, (6‐4) photolyase and blue‐light photoreceptors that were recently discovered in Arabidopsis thaliana, Sinapis alba and Chlamydomonas reinhardtii. Recently, we identified two human genes, hCRYl and hCRY2, belonging to this family. The proteins encoded by these genes have no DNA repair activity and therefore were hypothesized to function in human blue‐light response reactions. To identify downstream targets for these putative blue‐light photoreceptors we searched for interacting proteins by the yeast two‐hybrid method. We found that the tetratricopeptide repeat protein 1, Tpr1, and the protein serine/ threonine phosphatase 5 (PP5) that contains the TPR motif specifically interacted with hCRY2. The effect of the hCRY2‐PP5 interaction on the protein phosphatase activity was investigated. We found that hCRY2, but not the highly homologous (6‐4) photolyase, inhibits the phosphatase activity of PP5. This inhibition may be on the pathway of blue‐light signal transduction reaction in humans.
Biologically Active Radiation in the Vicinity of a Single Tree
Authors: Grant Richard H.
Published: January 2008

The horizontal photon flux density of photosynthetically active radiation (PAR) and flux density of ultraviolet A (UVA) and ultraviolet B (UVB) radiation were measured in the vicinity of isolated single trees during the summer of 1996. Measurements were made under shade and sunlit conditions along a transect aligned with the solar disk and the tree trunk. Flux density measurements were normalized by the flux density at a reference location away from the tree. Results showed (1) a more rapid decline in the flux density of UVA and UVB radiation than PAR with decreasing distance to the tree trunk on both the sunlit and shaded side of a tree and (2) more rapid changes in the flux density of UVB radiation UVA radiation, and PAR with distance from the tree on the sunlit side of the tree than the shaded side of the tree. The UVB/PAR ratio was found to increase in the shadow of a tree with increasing distance from the tree to between 4 and 6 for the conditions of the study. The potential for detrimental effects by UVB flux density under conditions of the high ratio may be mitigated by sunflecks at a given location over the course of a day.
Phytochrome Control of Anthocyanin Biosynthesis in Tomato Seedlings: Analysis Using Photomorphogenic Mutants
Authors: Kerckhoffs L. H. J. , Schreuder M. E. L. , Tuinen A. Van , Koornneef M. , Kendrick R. E.
Published: January 2008

Anthocyanin biosynthesis has been studied in hypocotyls and whole seedlings of tomato (Lycoperskon esculentum Mill.) wild types (WTs) and photomorphogenic mutants. In white light (WL)/dark (D) cycles the fri1 mutant, deficient in phytochrome A (phyA), shows an enhancement of anthocyanin accumulation, whereas the tri1 mutant, deficient in phytochrome Bl (phyBl) has a WT level of anthocyanin. Under pulses of red light (R) or R followed by far‐red light (FR) given every 4 h, phyA is responsible for the non‐R/FR reversible response, whereas phyBl is partially responsible for the R/FR reversible response. From R and blue light (B) pretreatment studies, B is most effective in increasing phytochrome responsiveness, whereas under R itself it appears to be dependent on the presence of phyBl. Anthocyanin biosynthesis during a 24 h period of monochromatic irradiation at different flu‐ence rates of 4 day‐old D‐grown seedlings has been studied. At 660 nm the fluence rate‐response relationships for induction of anthocyanin in the WT are similar, yet complex, showing a low fluence rate response (LFRR) and a fluence rate‐dependent high irradiance response (HIR). The high‐pigment‐1 (hp‐1) mutant exhibits a strong amplification of both the LFRR and HIR. The fri1 mutant lacks the LFRR while retaining a normal HIR. In contrast, a transgenic tomato line overexpressing the oat PHYA3 gene shows a dramatic amplification of the LFRR. The tri1 mutant, retains the LFRR but lacks the HIR, whereas the fri1, tri1 double mutant lacks both components. Only an LFRR is seen at 729 nm in WT; however, an appreciable HIR is observed at 704 nm, which is retained in the tri1 mutant and is absent in the fri1 mutant, indicating the labile phyA pool regulates this response component.
A Novel Aspect of Photodynamic Action: Induction of Recurrent Spikes in Cytosolic Calcium Concentration
Authors: Cui Zong Jie , Habara Yoshiaki , Wang Duo Yuan , Kanno Tomio
Published: January 2008

Effects of photodynamic action of gadolinium porphyrin‐like macrocycle B (PLMGdB) on cytosolic Ca2+ concentration, [Ca2+]c, was investigated in isolated rat pancreatic acini. The PLMGdB alone or light alone (2 min) had no effect on [Ca2+]c. Cell‐bound PLMGdB upon brief (0.5–2.0 min) light activation triggered recurrent spikes in [Ca2+]c. At lower PLMGdB concentration (100 nM) the spikes continued during the whole period of monitoring [Ca2+]c. At a higher concentration of 500 nM, the spikes continued for the first 40 min, followed by a gradual increase in basal [Ca2+]c upon which smaller spikes were superimposed. At 1, the spikes continued for the first 20 min, after that spiking gradually degenerated into a plateau phase. In many aspects, photodynamically triggered spikes resembled spikes generated by physiological concentrations of cholecystokinin. The spikes triggered by photodynamic action were likely to be the result of the ignition of a physiological “chain reaction”, because functional inositol‐1,4,5‐trisphosphate (IP3) receptors were required for spiking to occur. Two‐aminoe‐thoxydiphenylborate, an inhibitory modulator of IP3‐triggered Ca2+ release from intracellular stores, effectively inhibited photodynamically generated spikes. Therefore photodynamic action appears to be able to permanently transfix a physiological process, leading to long‐lasting pharmacological or therapeutic effects.
Correlation between Site ll‐Specific Human Serum Albumin (HSA) Binding Affinity and Murine in vivo Photosensitizing Efficacy of Some Photofrin Components
Authors: Tsuchida Takaaki , Zheng Gang , Pandey Ravindra K. , Potter William R. , Bellnier David A. , Henderson Barbara W. , Kato Harubumi , Dougherty Thomas J.
Published: January 2008

Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrina mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin® and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl‐L‐proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth
The Dynamics of Laser‐Induced Changes in Human Skin Autofluorescence—Experimental Measurements and Theoretical Modeling
Authors: Zeng Haishan , MacAulay Calum , McLean David I. , Palcic Branko , Lui Harvey
Published: January 2008

To study the temporal dynamics of human skin autofluorescence photobleaching, we measured the autofluorescence spectral changes of skin in vivo during continuous exposure to 442 nm (He‐Cd) laser light. Integral intensities were calculated for various spectral wavelength bands and plotted as a function of time. Mathematical analysis of the time function revealed a double‐exponential photobleaching process: I(t) = a exp(‐t/τ1,) + b exp(‐t/τ2) + c, in which t1, and t2 differed by an order of magnitude. A hypothesis for the mechanism of the double‐exponential photobleaching dynamics was proposed and evaluated using Monte Carlo modeling of light propagation in the skin and autofluorescence escape from skin. By combining the fluorophore microdistributions, Monte Carlo simulation results and the variation in fluorescence decrease parameters (a, b, c, τ1τ2) with increasing exposure intensities a biophysical explanation for the double‐exponential photobleaching function was elucidated. The fast decrease term corresponds to laser‐induced photobleaching in the stratum corneum, while the slow decrease term represents fluorophore changes in the dermis. The measured autofluorescence photobleaching dynamics can be used to determine the fractional contributions of different skin layers to the total autofluorescence signal measured in vivo.
In Vivo and In Vitro Photodynamic Studies with Benzochlorin Iminium Salts Delivered by a Lipid Emulsion
Authors: Garbo G. M. , Fingar V. H. , Wieman T. J. , III E. B. Noakes , Haydon P. S. , Cerrito P. B. , Kessel D. H. , Morgan A. R.
Published: January 2008

Benzochlorin iminium salts (Bis) are hydrophobic photosensitizers based on an octaethylbenzochlorin nucleus that absorb in the near‐IR region of the visible spectrum. In these studies the photodynamic activities of the zinc, copper and metal‐free BI derivatives were compared in vivo in C3H‐HeJ mice bearing a mammary adenocarcinoma tumor line. In vitro studies were also performed with the radiation‐induced fibrosarcoma tumor line. An argon‐pumped Ti‐sapphire laser tuned to deliver light between 710 and 800 nm or an Oriel arc‐lamp filtered to deliver broadband light above 590 nm were used as light source. A lipid emulsion was used as the delivery system for sensitizers in all studies. A pronounced solvent dependence was observed for the Q band for each of all iminium salts examined. As an example, the metal‐free (BI) derivative had an absorption maximum at 798 nm in dichloromethane and at 727 nm in serum. The action spectra showed a greater PDT response at blue‐shifted wavelengths for each of the three iminium salts both in vivo and in vitro. Among the three derivatives, the zinc analog (ZnBI) produced the greatest tumor regression at the low drug/light dose of 0.7 (μ mole/kg and 200 J/cm2. These results indicate that iminium salts have characteristics that may make them promising third‐generation photosensitizers.
Comparison of the DNA Damage Photoinduced by Fenofibrate and Ketoprofen, Two Phototoxic Drugs of Parent Structure
Authors: Marguery M. C. , Chouini‐Lalanne N. , Ader J. C. , Paillous N.
Published: January 2008

Fenofibrate and ketoprofen (KP) are two drugs of similar structure derived from that of benzophenone. Both are photoallergic and promote cross reactions in patients. However, the cutaneous photosensitizing properties of KP also include phototoxic effects and are more frequently mentioned. To account for this difference in their in vivo properties, their in vitro photosensitizing properties on DNA were compared. First, it was shown that under irradiation at 313 nm, fenofibric acid (FB), the main metabolite of fenofibrate, photosensitized DNA cleavage by a radical mechanism similar to that proposed for KP but with a 50 times lower efficiency. Furthermore, FB did not photosensitize the formation of pyrimidine dimers into DNA in contrast to KP, which did promote this type of DNA damage. Their difference in efficiency as DNA breakers was compared to their relative photochemical reactivity and the quantum yield of FB photolysis was found to be eightfold lower than that of KP. The reactivity of these drugs cannot explain alone the difference in their photosensitizing properties. Other factors such as the magnitude of the ionic character of the pho‐todecarboxylation pathway of these benzophenone‐like drugs are considered in the discussion.
Optical Absorption of Blood Depends on Temperature during a 0.5 ms Laser Pulse at 586 nm
Authors: Verkruysse Wim , Nilsson Annika M. K. , Milner Thomas E. , Beek Johan F. , Lucassen Gerald W. , van Gemert Martin J. C.
Published: January 2008

Optical properties are important parameters in port wine stain laser treatment models. In this study we investigated whether changes in blood optical properties occur during a 0.5 ms laser pulse. Blood from three volunteers was irradiated in vitro with laser pulses (radiant exposure 2–12 J cm−2, wavelength 586 nm, pulse length 0.5 ms). Reflection and transmission coefficients, measured using double integrating spheres, decreased slightly during the first part of the pulse. At 2.9 J cm−2 radiant exposure, the reflectance increased, independent of total radiant exposure of the pulse. This was caused by blood coagulation. A second sudden increase in reflection and a significant increase in transmission occurred near 6.3 J cm–2 and was accompanied by a "popping" sound, indicating rapid expansion of bubbles due to blood vaporization. A multilayered model of blood was used to fit calculated transmission coefficient curves to the measurements and determine temperature‐dependent optical blood absorption. Heat diffusion was shown to be of minor importance. A 2.5‐fold increase in absorption for temperatures increasing from 20 to 100°C, accurately describes transmission coefficients measured up to 2.9 J cm−2.
Factors Affecting Virus Photoinactivation by a Series of Phenothiazine Dyes
Authors: Wagner Stephen J. , Skripchenko Andrey , Robinette Daniel , Foley James W. , Cincotta Louis
Published: January 2008

A series of four phenothiazine dyes, including methylene blue (MB), were previously tested for their ability to photoinactivate viruses in red cell suspensions. One of the dyes, 1,9‐dimethyl‐3‐dimethylamino‐7‐dimethylaminophenothiazine (1,9‐dimethylmethylene blue), exhibited good intracellular and extracellular virucidal activity for several RNA and DNA viruses under conditions that minimally affected red cell properties. In order to understand why the virucidal specificity of 1, 9‐dhnethylmethylene blue was greater than other phenothiazines tested, the physical and chemical properties of the dye were compared to three other closely related analogues (MB, 1,9‐dimethyl‐3‐diethylamino‐7‐dlbutylaminophenothiazine [compound 4‐140], 1,9‐dimethyl‐3‐dimethylamino‐7‐diethylaminophenothiazine [compound 6‐136]). All compounds required light and oxygen for virucidal activity and had relatively high singlet oxygen yields (>0.5), but 1,9‐dimethylmethylene blue had a singlet oxygen yield approximately 50% greater than that of MB. In addition, the hydrophobicity/hydophilicity of the compounds varied, with the partition coefficients (2‐octanol : water) ranging from 0.11 for MB to 3560 for compound 4‐140. The dyes had the following affinities for DNA: 1,9‐dimethylmethylene blue > compound 6‐136 > MB ∼ compound 4‐140. This order was similar to the order of activities for photoinactivation of the nonenveloped bacteriophage, R17, by the four compounds. Results with the most hydrophobic compound, 4‐140, contrasted with those obtained with 1,9‐dimethylmethylene blue. Compound 4‐140 had a high affinity for protein and a low affinity for DNA. Although compound 4‐140 and light inactivated the nonenveloped bacteriophage R17 poorly, the dye readily photoinactivated enveloped viruses in buffer. However, unlike results with 1,9‐dimethylmethylene blue, viral inactivation of enveloped viruses by compound 4‐140 was completely inhibited by the presence of red cells and plasma. Thus, the high affinity of 1,9‐di‐methyymethylene blue for DNA and the dye's efficient singlet oxygen yield suggest viral nucleic acid as a potential target, which could explain the photosensitizer's ability to inactivate viruses without adversely affecting anuclete red cells.
Fluoroquinolone Antimicrobials: Singlet Oxygen, Superoxide and Phototoxicity
Authors: Martinez Lydia J. , Sik Robert H. , Chignell Colin F.
Published: January 2008

The fluoroquinolone antibacterial agents possess photo‐sensitizing properties that lead to phototoxic responses in both human and animal subjects. The phototoxicity order reported in humans is: fleroxacin > lomefloxacin, pefloxacin > ciprofloxacin ≫ enoxacin, norfloxacin and ofloxacin. Studies both in vivo and in vitro have related this phototoxicity to the generation of reactive oxygen species including hydrogen peroxide and the hydroxyl radical. We determined the quantum yields of singlet oxygen generation (φΔ,) by detection of the singlet oxygen (1O2) luminescence at 1270 tun for several fluoroquinolones, naphthyridines and other structurally related compounds. All the fluoroquinolones examined have low φΔ values ranging from 0.06 to 0.09 in phosphate buffer at pD 7.5. We also determined the 1O2 quenching constants for these compounds and their values were on the order of 106M−1 s1, except for lomefloxacin whose rate constant was 1.8 × 107M−1 s−1. The φΔ values were significantly decreased in a solvent of lower polarity such as methanol (0.007 ≤φΔ≤ 0.02). The production of 1O2 by these antibiotics did not correlate with the order reported for their phototoxicity. We also measured the photogeneration (λ > 300 nm) of superoxide by these antibacterials in dimethylsulfoxide using electron paramagnetic resonance and the spin trap 5,5‐dimethyl‐l‐pyrroiine N‐oxide. Although there is not a one‐to‐one correspondence between the relative rates of superoxide generation and the phototoxicity ranking of the fluoroquinolones, the more phototoxic compounds tended to produce superoxide at a faster rate. Nevertheless, the magnitudes of the observed differences do not appear sufficient to explain the range of fluoroquinolone phototoxicity potencies in human and animal subjects in general and the high activity of fleroxacin and lomefloxacin in particular. For these latter drugs the photoinduced loss of the F8 atom as fluoride and the concomitant generation of a highly reactive carbene at C‐8 provide a more plausible mechanism for their potent phototoxic and photocarcinogenic properties.
The Development of Solid Spectral Filters for the Regulation of Plant Growth
Authors: van Haeringen C. J. , West J. S. , Davis F. J. , Gilbert A. , Hadley P. , Pearson S. , Wheldon A. E. , Henbest R. G. C.
Published: January 2008

Phthalocyanine derivatives have been prepared and incorporated into polymer films for use as spectral filters for the modification of plant growth. The unusual absorption characteristics of phthalocyanines, notably the narrow absorption band in the visible region of the electromagnetic spectrum, allows the selective filtering of wavelengths necessary for excitation of either of the two isomeric phytochrome species. The resulting change in the photostationary state for the phytochrome is shown to have a marked effect on the growth characteristics of both chrysanthemums and antirrhinums. Chrysanthemums (short‐day plants) grown under a far‐red‐absorbing film showed a reduction in height (∼14%) and internodal length compared to those grown under a red‐absorbing film or a control with no absorption in the visible part of the spectrum; both leaf number and time to flowering were not affected by the presence of the spectral filter. For antirrhinums (long‐day plants) both a reduction in height and a substantial increase in leaf area (70%) of the plants grown under the far‐red‐absorbing film were observed, although flowering was delayed. The potential of these filters as replacements for chemical plant growth regulators is discussed.
Characterization of Photodegradation of Meta‐tetra (Hydroxyphenyl)chlorin (mTHPC) in Solution: Biological Consequences in Human Tumor Cells
Authors: Belitchenko I. , Melnikova V. , Bezdetnaya L. , Rezzoug H. , Merlin J.L. , Potapenko A. , Guillemin F.
Published: January 2008

The photobleaching of meta‐tetra(hydroxyphenyl)chlorin mTHPC) (irradiation wavelength 413 nm) in protein‐containing solution was evaluated by decay in absorbance in Soret band and in fluorescence (λexc= 423 nm, λem= 655 nm). Light exposure resulted in a decrease in absorption throughout the spectrum and simultaneous appearance of new absorption bands in the spectral region 325–450 nm. The rate of mTHPC photodegradation, followed by decay in absorbance, was 15‐fold lower than that observed in fluorescence. This fact reflects the photobleaching of presumably monomeric, fluorescing species of mTHPC. In order to determine the consequences of photobleaching of fluorescing mTHPC material on cellular uptake and photocytotoxicity, human HT29 colon adenocarcinoma cells were incubated with photobleached mTHPC during 5 h with or without following irradiation with the fixed fluence. Surprisingly, but up to the time when the fluorescence decreased by 50%, only a slight decrease in photocytotoxicity was detected. Either aggregated forms that have been taken up undergo intracellular monomerization (but we did not observe increase in fluorescence in living cells) or the photodynamic activity is mostly due to aggregates. The discrepancy of m‐THPC‐photodynamic therapy (PDT) effect and fluorescence measurements may suggest that aggregated m‐THPC plays an important role in mTHPC‐PDT.
Environmental Significance of Anthocyanins in Plant Stress Responses
Authors: Chalker‐Scott Linda
Published: January 2008

Abstract— Anthocyanins are water‐soluble pigments found in all plant tissues throughout the plant kingdom. Our understanding of anthocyanin biosynthesis and its molecular control has greatly improved in the last decade. The adaptive advantages of anthocyanins, especially in non‐reproductive tissues, is much less clear. Anthocyanins often appear transiently at specific developmental stages and may be induced by a number of environmental factors including visible and UVB radiation, cold temperatures and water stress. The subsequent production and localization of anthocyanins in root, stem and especially leaf tissues may allow the plant to develop resistance to a number of environmental stresses. This article reviews the environmental induction of anthocyanins and their proposed importance in ameliorating environmental stresses induced by visible and UVB radiation, drought and cold temperatures.
The Photochemical Attachment of the O‐Glucoside of 3‐Hydroxykynurenine to α‐Crystallin: A Model for Lenticular Aging
Authors: Dillon James , Skonieczna Monika , Mandal Krish , Paik David
Published: January 2008

Abstract— The young human lens contains a small metabolite from tryptophan called the O‐glucoside of 3‐hydroxykynurenine (3‐HKG). Its function is to absorb most radiation between 295 and 400 nm, preventing it from reaching the retina. With age the concentration of this component decreases while the lens crystallins acquire covalently attached chromophores. This study investigates the photochemical attachment of 3‐HKG to lens α‐crystallin. Initial studies showed that α‐crystallin photolyzed in the presence of 3‐HKG developed a fluorescence (emission, 440 nm) and UV‐visible spectrum similar to that found in aged human lens proteins. Extensive studies were then performed on the tryptic HPLC maps as monitored by photodiode array and fluorescent detection. Numerous photoproducts with either blue (emission, >400 nm) or green (emission, >500 nm) fluorescence were formed in addition to nonfluorescent compounds with absorption maxima above 300 nm. Comparisons were made between these model photoproducts and peptide maps from α‐crystallin isolated from old human lenses. In terms of retention time and UV‐visible spectra at least two of the peptides that appear in the model system are also present in the human samples. It is concluded that one of the aging processes in the human lens is the photochemically induced attachment of 3‐HKG to lens proteins.
Activation of Expression of the c‐fos Oncogene by UVA Irradiation in Cultured Human Skin Fibroblasts
Authors: Bose Biplab , Soriani Marco , Tyrrell Rex M.
Published: January 2008

Abstract— Both broad‐spectrum and near‐monochromatic (334 nm, 365 nm and 405 nm) UVA (320–380 nm) and near‐visible radiations strongly activate accumulation of mRNA corresponding to the nuclear oncogene and transcription factor, c‐fos, in cultured human skin fibroblasts within a dose‐range encountered in the environment. The oxidizing component of UVA is clearly of central importance to the activation observed because the absence of reduced glutathione strongly enhances the response. In contrast to observations in rodent cells, we observe negligible activation of the gene in human cells after UVB (290–320 nm) radiation. The results of this study provide evidence that UVA radiation strongly activates c‐fos gene expression in human dermal fibroblasts, a phenomena that is likely to be reflected in UVA‐mediated modulation of genes containing active AP‐1‐based enhancer elements in the promoter region.
Toxicology of a Boronated Porphyrin in Dogs
Authors: Tibbitts Jay , Fike John R. , Lamborn Kathleen R. , Bollen Andrew W. , Kahl Stephen B.
Published: January 2008

Abstract—Among the most important characteristics of any therapeutic agent are efficacy and an acceptable toxicity. Prior to human use, toxicity studies are performed in both small and large animal models. Our laboratory has developed a new binary therapy agent, a boronated porphyrin (BOPP), with excellent potential efficacy. The purpose of this study is to examine the toxicology of this compound in dogs. Sixteen dogs were given 35 mg/kg of BOPP intravenously and evaluated for up to 28 days following administration. Clinical and pathologic responses were measured. BOPP was clinically well tolerated with some cases of weight loss, vomiting and mild photosensitivity. Adverse effects were limited primarily to thrombosis at the administration site in several subjects and three cases of mild, possibly transient, liver injury. Clinical pathologic tests found reversible changes in white blood cell counts and platelets, with neither change being clinically significant. The low toxicity associated with BOPP as shown in this study provides valuable evidence supporting the use of BOPP in binary therapy.