bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemistry of 2,6‐D'ichlorodiphenylamine and 1‐Chlorocarbazole, the Photoactive Chromophores of Diclofenac, Meclofenamic Acid and Their Major Photoproducts
Authors: Encinas Susana , Bosca Francisco , Miranda Miguel A.
Published: January 2008

Diclofenac and meclofenamic acid are two structurally related nonsteroidal anti‐inflammatory drugs with some photosensitizing potential. Their photochemistry involves cyclization to monohalogenated carbazoles. In principle, photocyclization could occur by photodehalogenation, followed by intramolecular radical addition, or by 6TT electrocyclization and subsequent dehydrohalogenation of the intermediate dihydrocarbazoles. Previously, it has been assumed that the reaction follows the first pathway and that the key species associated with phototoxicity are the resulting aryl radicals. In the present work, we have performed photophysical and photochemical studies on 2,6‐dichlorodiphenylamine (la). This is a suitable model compound because since it contains the active chromo‐phore present in diclofenac and meclofenamic acid, and its photoreactivity should be relevant to the understanding of the photobiological properties of both drugs. Our results clearly show that the first photochemical reaction is a very rapid 6iT‐electrocyclization, and hence no radicals are formed at this stage. Instead, cleavage of the carbon‐halogen bond occurs in the 1‐chlorocarbazole photoproduct 2a. The reduced lifetime of the 2a triplet (as compared with the unsubstituted carbazole) and the observed reaction quenching by oxygen are in agreement with the reaction occurring from the excited triplet state. Overall, the above results suggest that the potential phototoxicity of diclofenac and meclofenamic acid is due to a photobiologically active photoproduct that is able to generate radicals upon photolysis, rather than to the parent drug.
Supramolecular Cationic Tetraruthenated Porphyrin and Light‐Induced Decomposition of 2‐Deoxyguanosine Predominantly Via a Singlet Oxygen‐Mediated Mechanism
Authors: Ravanat Jean‐Luc , Cadet Jean , Araki Koiti , Toma Henrique E. , Medeiros Marisa H. G. , Mascio Paolo Di
Published: January 2008

The tetraruthenated porphyrin, u.‐[/wes0‐5,1O,15,2O‐tet‐ra(pyridyl)porphyrin]tetrakis[ftis‐(bipyridine)chloride ruthenium(II)] (TRP) is a supramolecular cationic species. The aim of the present investigation was to evaluate the photodynamic properties of TRP and Zn‐TRP to damage DNA with emphasis on the mechanistic aspects. The ability for tetraruthenated porphyrin derivatives to induce photosensitization reactions has been determined using 2′‐deoxyguanosine as a DNA model compound. The main photooxidation products of the targeted nucleoside were identified and classified according to their mechanisms of formation, involving either a radical pathway (type I) or a singlet oxygen‐mediated mechanism (type II). Quantification of the different oxidation products provides a means to evaluate the relative contribution of type I and type II pathways associated with the oxidative photosensitization of 2′‐deoxyguanosine by tetraruthenated porphyrin derivatives. Results indicate that x02 plays a major role in the mechanism of photooxidation mediated by these porphyrin derivatives. In addition an increase of the photosensitizing effect in the presence of zinc is observed. For each sensitizer, the ratio between type II and type I photoproducts has been calculated and compared to that of other known dyes such as methylene blue and riboflavin.
Effects of Charge and Structure of Hyaluronic Acid on the Luminescence Quenching in Aqueous Solution
Authors: Kluge Thomas , Masuda Akiko , Yamashita Koichi , Ushida Kiminori
Published: January 2008

The quenching of electronically excited Ru(bpy)32+ (bpy = Tris‐2,2′‐bipyridine) by methylviologen (MV) and ferricyanide (FC) in aqueous solutions of hyaluronic acid (HA) was studied. The structural and viscosity changes occuring with increasing HA concentration were found to influence the photophysical and photochemical properties of the sensitizer. Different kinetic models had to be used for the quenchers studied. The kinetics of the quenching of *Ru(bpy)32+ by MV can be described by the pseudophase model, which indicates that the rate for the exchange of the quencher between the microdroplets is higher than that for the excited state decay of the Ruthenium complex. In contrast, the quenching by the negatively charged quencher, FC, can be described by the Infelta‐Tachiya equation, which indicates that the distribution of this quencher on the aqueous microdroplets is of the Poisson type and there is no exchange of quencher molecules during the lifetime of the sensitizer. The lifetimes of the excited Ruthenium complex, the unimolecular constants for its quenching by FC and the average concentration of the aqueous microdroplets increase with increasing HA concentration, reflecting the change in the solution structure during the transition from semidilute to concentrated regions. For MV no significant dependence of the quenching constant on the HA content of the solution was found. The reaction behavior of charged reactants in HA solution depends strongly on the sign of the charge.
Glutathione Synthesis Is Not Involved in Protection by N‐Acetyl cysteine Against UVB‐lnduced Systemic Immunosuppression in Mice
Authors: Steenvoorden David P. T. , van Henegouwen Gerard M. J. Beijersbergen
Published: January 2008

Abstract— Irradiation of the skin with ultraviolet‐B (UVB) radiation causes a local and systemic suppression of T‐cell‐medi‐ated immune responses. Recently, N‐acetylcysteine (NAC) was found to protect against UVB‐induced immunosuppression and several other types of UV damage. The protective effects appeared to be based on the ability of NAC to increase glutathione (GSH) levels by promoting GSH synthesis. In this study, it was investigated whether topical application of NAC was still effective against UVB‐induced suppression of contact hypersensitivity if GSH synthesis was blocked. Mice were pretreated with buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, which succeeded in blocking the increase in epidermal GSH after topical application of NAC. Whereas the non‐BSO‐treated animals showed an increase to around 155% of the control GSH level for all NAC doses tested, only a slight (nonsignificant) increase in epidermal GSH was observed in the BSO‐treated animals. Surprisingly, the protective efficacy of NAC against UVB‐induced immunosuppression was not affected by the BSO pretreatment. No significant difference between the protective efficacy of NAC in the two groups was observed. Apparently, the antioxidant effect of NAC itself was sufficient to provide protection against UVB‐immunosuppression, independent of GSH synthesis.
The Effects of Serum on Cellular Uptake and Phototoxicity of Mono‐L‐Aspartyl Chlorin e6 (NPe6) In Vitro
Authors: Sheyhedin Llyar , Aizawa Katsuo , Araake Minako , Kumasaka Hideo , Okunaka Tetsuya , Kato Harubumi
Published: January 2008

Abstract— Previous reports showed that the photosensitizer mono‐l‐aspartyl chlorin e6 (NPe6) binds to serum proteins. However, the influence of this binding on the cellular uptake and photodynamic therapy (PDT) phototoxicity of NPe6 is still undefined. In this paper, we studied how serum in medium affected the P388 cellular uptake and PDT phototoxicity of NPe6 in vitro. This was assessed by (1) detection of the red shift (654 nm Q band peak of absorption) induced by protein binding NPe6; (2) detection of intracellular concentration of NPe6 by HPLC and (3) measurements of the cell survival ratio after PDT by MTT assay. The 654 nm Q band peak of NPe6 shifted to 665 nm after binding of NPe6 and serum proteins. The protein‐bound NPe6 cannot be uptaken by cells, thus there was no PDT phototoxicity. Nevertheless, phototoxicity recovered when the concentration of NPe6 excessed the serum protein binding ability or there was free serum protein in the medium. These data suggested that the cellular uptake of NPe6 is inhibited by serum components in the medium, and that only free NPe6 is accumulated by P388 cells even during relatively long incubations. The cytotoxicity of PDT mainly depends on the free NPe6 level in the medium.
Optical Doppler Tomography: Imaging in vivo Blood Flow Dynamics Following Pharmacological Intervention and Photodynamic Therapy
Authors: Chen Zhongping , Milner Thomas E. , Wang Xiaojun , Srinivas Shyam , Nelson J. Stuart
Published: January 2008

A noninvasive optical technique has been developed for imaging in vivo blood flow dynamics and vessel structure with high spatial resolution. The technique is based on optical Doppler tomography, which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations in turbid biological tissue. Applications of this technique for monitoring changes in blood flow dynamics and vessel structure following pharmacological intervention and photodynamic therapy are demonstrated.
Luminol Oxidation by Hydrogen Peroxide Catalyzed by Tobacco Anionic Peroxidase: Steady‐State Luminescent and Transient Kinetic Studies
Authors: Gazaryan Irina G. , Rubtsova Maya Yu. , Kapeliuch Yuri L. , Rodriguez‐Lopez José Neptuno , Lagrimini L. Mark , Thorneley Roger N. F.
Published: January 2008

The properties of a newly isolated anionic tobacco peroxidase from transgenic tobacco plants overexpressing the enzyme have been studied with respect to the chemiluminescent reaction of luminol oxidation. These were compared to the properties of horseradish peroxidase in the cooxidation of luminol and p‐iodophenol, the enhanced chemiluminescence reaction. The pH, luminol and hydrogen peroxide concentrations were optimized for maximum sensitivity using the tobacco enzyme. The detection limit for the latter under the optimal conditions (2.5 mM luminol, 2 mM hydrogen peroxide, 100 mM Naborate buffer, pH 9.3) was about 0.1 pM, which is at least five times lower than that for horseradish peroxidase in enhanced chemiluminescence with p‐iodophenol. The rate constants for the elementary steps of the enzyme‐catalyzed reaction have been determined: k1= 4.9 × 106M−1 s1, k2= 7.3 × 106M−1 s−1, k3= 2.1 × 106M−1 s−1 (pH 9.3). The similarity of these rate constants is unusual for plant peroxidases. The high catalytic activity of tobacco peroxidase in the luminescent reaction is explained by the high reactivity of its Compound II toward luminol and the high stability of the holoenzyme with respect to heme dissociation. This seems to be a unique property of this particular enzyme among other plant peroxidases.
Regulation of Stimulated Cyclic AMP Synthesis by Urocanic Acid
Authors: Bouscarel Bernard , Noonan Frances , Ceryak Susan , Gettys Thomas W. , Phillips Terry M. , DeFabo Edward C.
Published: January 2008

Urocanic acid (UCA) has been shown to mediate the UVB radiation‐induced immunosuppression initiated i’the skin by UV‐induced isomerization from the trans to the cis isomer. However, the mechanism by which cis. UCA acts is still unclear. Therefore, the present stud was undertaken to determine the effect of trans‐ and cis UCA on cyclic adenosine 3′,5′‐monophosphate (cAMP synthesis in human dermal fibroblasts, Golden Syria’hamster hepatocytes and in the human adenocarcinoms cell line, HT29. Neither trans‐ nor cis‐UCA was able is stimulate cAMP synthesis directly in any of the model: tested. In human dermal fibroblasts, cis‐UCA, in contras to trans‐UCA, specifically inhibited cAMP synthesis in duced by either prostaglandin (PG) El or PGE2 with s maximum inhibitory effect of 25‐30% at cis‐UCA con centrations greater than 1 μM and half‐maximum inhib itory effect (ECso) observed at 35 nM. The effect of cis‐UCA was not to stimulate phosphodiesterase and cAMP breakdown. The inhibitory effect of cis‐UCA (an imid azole derivative) was not mediated through stimulatiot of the α2‐adrenergic receptor. The inhibitory effect of cis UCA on stimulated cAMP synthesis was a function of the cell density and was only significant when the fibroblast were confluent or postconfluent. In contrast to the studie with human dermal fibroblasts, an inhibitory effect of cis‐UCA was not observed in either isolated hamster he patocytes or HT29 cells, in which cAMP synthesis wa stimulated by glucagon and vasoactive intestinal peptide respectively. These results point to a possible regulation of cAMP synthesis in fibroblasts as one mechanism by which cis‐UCA exerts its biological effect in the skin.
Ultraviolet B Irradiation Modulates the Immune System of Fish (Rutilus rutilus, Cyprinidae). I. Phagocytes
Authors: Salo Harri M. , Aaltonen Tuula M. , Markkula S. Eveliina , Jokinen E. Ilmari
Published: January 2008

Roach (Rutilus rutilus) were irradiated with a single dose of ultraviolet B (UVB) radiation (0.4 J/cm2) in order to study the effects of UVB on the nonspecific immune defense mechanisms of fish. Neutrophils and macrophages were isolated from the head kidney of fish on days 1–14 postirradiation. Both random and directed migration of neutrophils, studied by migration under agarose assay, were suppressed on day 1 after UVB irradiation. The respiratory burst of phorbol 12‐myristate 13‐acetatestimulated neutrophils and macrophages was also suppressed at days 1 and 2 after UVB irradiation. The suppression of migration and respiratory burst were restored or the responses were even enhanced later, but on the other hand spontaneous cytotoxicity of neutrophils toward 51chromium‐labeled K562 target cells stayed suppressed throughout the 14 day follow‐up. This study indicates that UVB radiation has the potential to suppress the functioning of phagocytes and to compromise the immune system of fish.
Kinetics of Photobleaching of Protoporphyrin IX in the Skin of Nude Mice Exposed to Different Fluence Rates of Red Light
Authors: Sorensen Roar , Lani Vladimir , Moan Johan
Published: January 2008

Abstract— The purpose of the present study was to determine the kinetics and the fluence rate dependency of the photo‐bleaching of protoporphyrin IX (PpIX) in normal skin of Balb/c nude mice after systemic and topical application of 5‐aminolevulinic acid (ALA). ALA was administered systemically (200 mg/kg body weight, i.p.) and topically (20% w/w ALA cream) to the mice. Fluences of up to 40 J/cm2 were delivered by a dye laser (636 nm) at fluence rates of 37.5, 75, 150, 300 and 500 mW/cm2. The photo‐bleaching rate was constant within this range of fluence rates. This result suggests that there is no oxygen effect for PpIX photobleaching in this region for the skin of Balb/c nude mice. During light exposure the fluorescence decay followed neither first‐ nor second‐order kinetics. The decay rate was slightly faster after systemic application than after topical application of ALA, but did not depend on the time (1–8 h) between application and analysis.
Singlet Oxygen‐Versus Nonsinglet Oxygen‐Mediated Mechanisms of Sensitizer Photobleaching and Their Effects on Photodynamic Dosimetry
Authors: Georgakoudi Irene , Foster Thomas H.
Published: January 2008

We report the effects of singlet oxygen (1O2) and non‐1O2‐mediated sensitizer photobleaching on oxygen consumption and dosimetry during photodynamic therapy (PDT) of sensitized multicell tumor spheroids. We develop a theoretical model for the description of non‐1O2‐mediated photobleaching resulting from irreversible reactions of the excited singlet or triplet sensitizer populations with cell substrate. We show that the fluence‐dependent simple exponential decay expression of sensitizer degradation is not consistent with these mechanisms and, therefore, with any reasonable mechanism that we consider, because we have shown previously that 1O2‐mediated photobleaching cannot be described by a simple exponential with a constant photobleaching coefficient (I. Georgakoudi et al., Photochem. Photobiol. 65, 135–144, 1997). Analysis of oxygen microelectrode measurements performed at the edge of Nile blue selenium (EtNBSe)‐and protoporphyrin IX (PpIX)‐sensitized spheroids during PDT demonstrates that the former drug photobleaches via a non‐1O2‐mediated mechanism, while the latter is degraded via a 1O2‐mediated mechanism. Comparisons of the cytotoxic effects of EtNBSe with those of Photofrin® (a drug that is degraded via a 1O2‐mediated mechanism) indicate that the lower threshold 1O2 dose and the higher extinction coefficient and 1O2 yield for EtNBSe do not necessarily result in improved photodynamic effects, thus emphasizing the importance of the sensitizer photo‐bleaching mechanism for dosimetry.
Photoprotection by Topical DMA Repair Enzymes: Molecular Correlates of Clinical Studies
Authors: Yarosh Daniel B. , O'Connor Adrienne , Alas Lori , Potten Christopher , Wolf Peter
Published: January 2008

Abstract— A new approach to photoprotection is to repair DNA damage after UV exposure. This can be accomplished by delivery of a DNA repair enzyme with specificity to UV induced cyclobutane pyrimidine dimers into skin by means of specially engineered liposomes. Treatment of DNA‐repair‐deficient xeroderma pigmentosum patients or skin cancer patients with T4N5 liposome lotion containing such DNA repair liposomes increases the removal of DNA damage in the first few hours after treatment. In these studies, a DNA repair effect was observed in some patients treated with heat‐inactivated enzyme. Unexpectedly, it was discovered that the heat‐inactivated T4 endonuclease V enzyme refolds and recovers enzymatic activity. These studies demonstrate that measurements of molecular changes induced by biological drugs are useful adjuvants to clinical studies.
The Electronic Structure of Carcinogenic Dibenzopyrenes: Linear Dichroism, Fluorescence Polarization Spectroscopy and Quantum Mechanical Calculations
Authors: Andersen Kristine B. , Waluk Jacek , Thulstrup Erik W.
Published: January 2008

Abstract—In studies of polycyclic aromatic hydrocarbon carcinogenicity three dibenzopyrenes have been named as the strongest mutagens together with the frequently studied benzo[a]pyrene. A detailed study of the electronic structure of one of the three compounds, dibenzo [a, i] pyrene, was performed several years ago. Here we present a similar study of the two remaining compounds, dibenzo [a, h] pyrene and dibenzo [a, e] pyrene. The studies include electronic linear dichroism spectra, fluorescence polarization spectra and quantum mechanical calculations for both molecules, as well as vibrational linear dichroism spectra for the former of the two.
Effect of Mammalian Cell Differentiation on Response to Exogenous 5‐Aminolevulinic Acid
Authors: Li Ge , Szewczuk Myron R. , Pottier Roy H. , Kennedy James C.
Published: January 2008

Abstract— Many different types of mammalian cells accumulate fluorescing and photosensitizing concentrations of protoporphyrin IX (PpIX) when exposed to exogenous 5‐aminolevulinic acid (ALA) in vivo or in vitro. Most types of malignant cells accumulate substantially more ALA‐induced PpIX than do the normal cells from which they arose. Most types of malignant cells also are less differentiated than their normal counterparts. We therefore considered the possibility that malignant cells demonstrate a malignant ALA phenotype (accumulate abnormally large amounts of PpIX when exposed to exogenous ALA) as a direct consequence of their less differentiated state. Human promyelocyte cell line HL‐60 and mouse preadipocyte cell line 3T3 L1 were induced to differentiate by exposing them to inducing agents in vitro. The HL‐60 cells accumulated less ALA‐induced PpIX when differentiated, but the 3T3 L1 cells accumulated more. It appears then that changes in the ALA phenotype with changes in the state of differentiation are cell‐type specific. The decreased accumulation of ALA‐induced PpIX that accompanied differentiation of the promyelocytic leukemia cells may have clinical application for rapid quantitation of the response of myelocytic leukemia patients to differentiation therapy.
Artificial Light‐Harvesting Antennae: Singlet Excitation Energy Transfer from Zinc Chlorin Aggregate to Bacteriochlorin in Homogeneous Hexane Solution
Authors: Miyatake Tomohiro , Tamiaki Hitoshi , Holzwarth Alfred R. , Schaffner Kurt
Published: January 2008

Abstract— Zinc chlorins possessing 31‐hydroxyl and 131‐carbonyl groups self‐assemble in nonpolar solvents, such as hexane, in a manner similar to bacteriochlorophyll c in the chlorosomes of green photosynthetic bacteria. Visible absorption and steady‐state fluorescence measurements of zinc chlorin aggregates containing a small amount of the bacteriochlorin‐zinc chlorin dyad molecules showed that singlet excitation energy transfer from the zinc chlorin aggregate to the bacteriochlorin moiety of the coaggre‐gated dyad occurs in the homogeneous solution. In the coaggregated dyad, the bacteriochlorin moiety plays the role of an efficient energy trap and the chlorin moiety the role of an anchor to the donor aggregate. The artificial assembly thus mimics the structure and function of natural chlorosomes and can be considered as the first in vitro supramolecular light‐harvesting antenna.
Spacer Length Effect on the Photoinduced Electron Transfer Fluorescent Probe for Alkali Metal Ions
Authors: Ji Hai‐Feng , Dabestani Reza , Brownxy Gilbert M. , Hettich Robert L.
Published: January 2008

Abstract— We have synthesized four derivatives of aikyi pyrene covalently bonded to aza‐lS‐crown‐6 at the nitrogen position, Py(CH2)n, (n = 1–4), to study the effect of spacer length on the emission properties of pyrene fluorophore upon complication of alkali metal ions by the crown moiety. In the absence of alkali metal ions, the parent molecule is weakly fluorescent because its emission is partially quenched by photoinduced electron transfer (PET) from nitrogen lone pairs to the excited singlet state of pyrene. Complication of alkali metal ions (e.g. K+) by the crown moiety prevents the nitrogen lone pair from participating in PET and results in an enhancement in the observed emission from pyrene (fluorescent turn on). Because the PET effect could be exerted through bonds as well as space, its magnitude may show a dependence on chain length. We have examined the fluorescence behavior of these pyrene aza‐crown ether derivatives in the presence of alkali metal ions to determine the magnitude of such an effect and its impact on the sensitivity of the fluorescent probe for detection purposes. Our results indicate that maximum efficiency for PET between the pyrene moiety and aza‐crown ether is achieved when n ≤ 3.
Research Note: Ultraviolet Irradiation (UVB) Interrupts Calcium Cell Signaling in Lens Epithelial Cells
Authors: Hightower Kenneth R. , Duncan George , Dawson Allan , Wormstone I. M. , Reddan John , Dziedizc Dorothy
Published: January 2008

Abstract— A preliminary study was undertaken to establish whether low‐dose UV irradiation (UVB) affects calcium cell signaling in rabbit lens epithelia. In a suspension of lens epithelial cells (line NN1003A), changes in intracellular Ca2+ were measured by Fura‐2 fluorescence in response to exogenously added ATP. The cellular response to ATP, referred to as the calcium signal, is characterized by a brief increase and subsequent decrease in cytosolic Ca2+ levels. Ultraviolet B irradiation (1.8–9 mJ/cm2) was found to reduce the magnitude of the Ca2+ signal in a dose‐dependent manner. A 5 min UVB exposure (9 mJ/cm2) completely altered the biphasic nature of the calcium signal, causing only an immediate and steady rise in cytosol Ca2+ levels. Lower fluences of UVB irradiation (2 min exposure times or 3.6 mJ/cm2) induced a 50% reduction in the calcium signal. When irradiated cells were returned to culture for 3 h after irradiation, calcium signals induced by ATP were normal. In view of the photooxidative nature of UVB irradiation, the oxidative state of cells was assessed by measuring glutathione (GSH) levels. Ultraviolet B irradiation caused a rapid 20% decline in GSH levels that returned to near‐control values after a 3 h postirradiation incubation. The results of this study indicate that fluences lower than previously found to be cataractogenic can perturb calcium cell signaling in cultured lens epithelial cells.
Excited‐State Properties of Thymidine and Their Relevance to Its Heterogeneous Emission in Double‐Stranded DNA
Authors: Georghiou S. , Gerke L. Stacy
Published: January 2008

Abstract— Published results on synthetic polynucleotides point to T as the major emitting fluorophore in DNA. We have reported also that the bases of the nonalternating polynucleotide poly(dA).poly(dT), in which T was selectively excited, undergo large‐amplitude motions on the picosecond‐nanosecond time scales (S. Georghiou et al., Biophys. J. 70, 1909–1922, 1996). In that study, the fluorescence decay profile of the T bases of this polynucleotide was found to contain a number of components; these may be considered to be the result of the motions of the bases that give rise to a distribution of stacked geometries of varying rigidity as well as dispersion and polar interactions. Here, we report the results of a study that we have undertaken in order to test this hypothesis. To this effect, we have studied the photophysical properties of thyntidine (1) in aqueous buffer and in a number of organic solvents and (2) in aqueous sucrose solutions of viscosity extending to 149 cP. The results suggest that the fluorescence quantum yield decreases with an increase in the polarizability of the solvent, whereas it increases with an increase in the solvent polarity (on the basis of the empirical parameter of solvent polarity ENT) or viscosity. These findings suggest the following for the photophysical properties of the T bases in DNA: (1) Base stacking results in two antagonistic effects, namely it causes a reduction in fluorescence as a result of dispersion interactions and an enhancement as a result of a reduction in the motions of the bases and (2) exposure of the bases to the aqueous environment results in fluorescence enhancement.
Photoionization of Ferrocytochrome c by 248 nm Laser Light and the Observation of the Early Stages of Ferricytochrome c Unfolding in the Nanosecond‐to‐millisecond Timescale
Authors: Candeias Luis P. , Steenken Steen
Published: January 2008

Abstract— Photolysis of ferrocytochrome c by 248 nm laser light in aqueous solution at pH 7 generates hydrated electrons (eaq‐) by a monophotonic process with quantum yield φ= 0.034. Approximately three‐quarters of the eaq‐ originate from the heme, which is converted from the ferrous to the ferric state in <100 ns. The conformational changes associated with the change in the redox state of cytochrome c are either not detectable spectrophotometrically or complete in <100 ns. Also, under conditions where ferrocytochrome c is stable but ferricytochrome c is unfolded (3 M guanidine, pH 7, 40°C), photoionization of ferrocytochrome c generated ferricytochrome c with similar quantum yield. Under these conditions, the lifetime of native ferricytochrome c is 67 μs; it decays via two intermediates with Λmax > 410 nm, neither of which is the thermodynamically favored, unfolded form. These species are putatively identified as unfolding intermediates with normative iron ligands, similar to those found during folding of ferrocytochrome c. The results suggest that unfolding, like folding, proceeds by intrachain diffusion and ligand exchange.
Enhancement of ALA‐PDT Damage by IR‐lnduced Hyperthermia on a Colon Carcinoma Model
Authors: Orenstein A. , Kostenich G. , Kopolovic Y. , Babushkina T. , Malik Z.
Published: January 2008

Abstract— The interaction of photodynamic therapy (PDT) with 5‐aminolevulinic acid (ALA) and hyperthermia is not well understood. In the present study, significant enhancement of tumor damage was observed after simultaneous application of ALA‐PDT and IR‐induced hyperthermia using a broad‐band incoherent light source. One hour after systemic administration of ALA at a dose of 200 mg/kg, subcutaneously transplanted C26 colon carcinoma tumors were irradiated with two bands of the VersaLight® system, red (R, 580–720 nm) and red plus IR (R+IR, 580–720 nm and 1250–1600 nm). Photoirradiation using the R+IR band at different fluence rates and exposures caused mild heating of the tumor to 39–43°C at a 3 mm depth. Electron microscopy after ALA+R, ALA+R+IR and R+IR treatments showed early mitochondrial swelling that was more pronounced in the ALA+R+IR group. Tumor necrosis assessment, using histology and vital staining, revealed an enhancement of tumor necrosis depth in the ALA+R+IR group compared to ALA+R and R+IR. The results showed that subhyperthermic heating to 39–39.5°C in the ALA+R+IR group decreased the threshold light dose required for 100% tumor necrosis from 210 J/cm2 (observed in the ALA+R group) to 140 J/cm2. A tumor growth delay test, based on tumor volume measurement, also revealed significant enhancement of antitumor effect after application of ALA+R+IR compared to ALA+R.
Highly Selective Targeting of Ovarian Cancer with the Photosensitizer PEG‐m‐THPC in a Rat Model
Authors: Hornung Rene , Fehr Mathias K. , Monti‐Frayne Jill , Krasieva Tatiana B. , Tromberg Bruce J. , Berns Michael W. , Tadir Yona
Published: January 2008

Photodynamic therapy (PDT) uses light to activate a photosensitizer that has been absorbed or retained preferentially by cancer cells after systemic administration. The first pegylated photosensitizer, tetrakis‐(m‐methoxypo‐lyethylene glycol) derivative of 7,8‐dihydro‐5,10,15,20‐te‐trakis(3‐hydroxyphenyl)‐21,23‐[H]‐porphyrin (PEG‐m‐THPC), was evaluated to target selectively unresectable pelvic ovarian cancer bulks. Our goals were two‐fold: (1) to establish an ovarian cancer model suitable for the development of debulking techniques and (2) to characterize the pharmacokinetics and tumor selectivity of PEG‐m‐THPC by fluorescence microscopy. NuTu‐19 ovarian cancer cells were injected into the caudal part of the right psoas muscle of Fisher rats. Five weeks later, 30 mg/kg body weight of PEG‐m‐THPC was injected intravenously. Necropsy was performed between 4 and 10 days following drug application, and fluorescence of the tumor and various abdominal organs was measured. All rats developed bulky pelvic tumors with an average diameter of 2.6 cm (± 0.6 SD). Tumor masses were encompassing and infiltrating pelvic organs in a similar manner to ovarian cancers in humans. Fluorescence of cancer tissue was maximal 8–10 days following drug application. At 8 days, the tumor‐to‐tissue ratio was 40:1 (plusmn; 12 SE) for most abdominal organs. We conclude that this tumor model may be used for the study of new pelvic debulking techniques, and that the tumor selectivity of PEG‐m‐THPC is exceptionally high 8 days after drug application. Based on these data, we are currently developing a PDT‐based minimally invasive debulking technique for advanced ovarian cancer.
Photophysical Properties of Rufloxacin in Neutral Aqueous Solution
Authors: Sortino Salvatore , Marconi Giancarlo , Giuffrida Salvatore , Guidi Guido De , Monti Sandra
Published: January 2008

The photophysical properties of rufloxacin, 9‐fluoro‐2r3‐dihydro‐10‐(4‐methyl‐l‐pyrazinyl)‐7‐oxo‐7‐H‐pyri‐do[l,2,3‐de]‐l,4‐benzothiazin‐6‐carboxylic acid, a fluoroquinolone antibacterial drug exhibiting photosensitizing action toward biological substrates, were studied in aqueous solutions at neutral pH. The lowest excited electronic states of the zwitterion were characterized by both experimental techniques and theoretical methods. Steady‐state and time‐resolved emission, triplet‐state absorption and singlet oxygen production were investigated. The results indicate that the lowest excited singlet is a fluorescent, relatively long‐lived state (φr= 0.075, Tr≅ 4.5 ns) with an efficient intersystem crossing to the triplet manifold (φisc≅ 0‐7)‐ The lowest triplet is a long‐lived state (TT≅ 10 μs at 295 K in 0.01 M phosphate buffer), with properties that make it a good candidate for being the precursor of the photodecarboxylation of the drug. It is quenched by oxygen at a rate of 1.7 times 109M‐1 s‐1 and singlet oxygen is formed with a quantum yield of 0.32 in air‐saturated solutions.
In Vivo Application of Intestinal pH Measurement Using 2,7‘‐Bis(carboxyethyl)‐5,6‐carboxyfluorescein (BCECF) Fluorescence Imaging
Authors: Maréchal Xavier , Mordon Serge , Devoisselle Jean Marie , Bégu Sylvie , Guery Benoit , Neviére Rémi , Buys Bruno , Dhelin Guy , Lesage Jean Claude , Mathieu Daniel , Chopin Claude
Published: January 2008

Measurement of gastrointestinal intramucosal pH (pH,m) has been recognized as an important factor in the detection of hypoxia‐induced dysfunctions. However, current pH measurement techniques are limited in terms of time and spatial resolutions. A major advance in accurate pH measurement was the development of the ratiometric fluorescent indicator dye, 2′,7′‐bis(carboxyethyl)‐5,6‐car‐boxyfluorescein (BCECF). This study aimed to set up and validate a fluorescence imaging technique to measure in vivo the intramucosal pH (pHim) of the intestine. The intestine was inserted into an optical chamber placed under a microscope. Animals were injected intravenously with the pH‐sensitive fluorescent dye BCECF. Fluorescence was visualized by illuminating the intestine alternately at 490 and 470 nm. The emitted fluorescence was directed to an intensified camera. The ratio of emitted fluorescence at excitation wavelengths of 490 and 470 nm was measured, corrected and converted to pHim by constructing a calibration curve. The pHim controls were performed with a pH microelectrode and were correlated with venous blood gas sampling. Results show that pHim is determined with an accuracy of ± 0.07 pH units and a response time of I min. In conclusion pHim mapping of rat intestine can be obtained by fluorescence imaging using BCECF. This technology could be easily adapted for endoscopic pH measurements.
Base‐specific Photocleavage of DNA Induced by Pazelliptine Sensitization: Study of the Mechanism by Time‐resolved Absorption and Fluorescence
Authors: Fontaine‐Aupart Marie‐Pierre , Renault Eric , Videlot Christine , Tfibel Francis , Pansu Robert , Charlier Michel , Pernot Pascal
Published: January 2008

The intercalating antitumoral drug pazelliptine (PZE) is able to photosensitize the formation of single‐ and double‐strand breaks in supercoiled plasmid DNA and selective photocleavage at guanine residues is observed. In order to understand the mechanisms of DNA cleavage mediated by the photoexcited drug, singlet and triplet excited‐state processes in PZE complexed with poly(dA‐dT)‐poly(dA‐dT), poly(dG‐dC)‐poly(dG‐dC) and calf thymus DNA have been investigated by means of single photon counting fluorescence decay and transient absorption techniques. For each complex, three different binding sites have been identified, due to the existence of different geometric structures of the drug in the ground state. For one type of binding site, a proton transfer reaction occurs in the singlet excited state whatever the nucleic acid environment. In contrast, the relaxation dynamics for the other two sites are found to depend widely upon the type of polynucleotide in which the drug has been intercalated. From the results of this study, we suggest that the photodynamic action of PZE does not originate from excitation of the drug in the environment of G‐C base pairs but is initiated from its triplet state that reacts by electron transfer with the adenine bases. The specificity of cleavage could be the result of subsequent reactions leading to guanine oxidation.
Calcyclin-Binding Protein Inhibits Proliferation, Tumorigenicity, and Invasion of Gastric Cancer
Authors: Ning Xiaoxuan , Sun Shiren , Hong Liu , Liang Jie , Liu Lili , Han Shuang , Liu Zhiguo , Shi Yongquan , Li Yuan , Gong Weiqin , Zhang Shanhong , Chen Yu , Guo Xueyan , Cheng Yi , Wu Kaichun , Fan Daiming
Published: January 2008

Calcyclin-binding protein/Siah-1–interacting protein (CacyBP/SIP), a target protein of the S100 family, which includes S100A6, S100A1, S100A12, S100B, and S100P, has been identified as a component of a novel ubiquitinylation complex leading to β-catenin degradation. However, the function of CacyBP/SIP in gastric cancer has not been elucidated. In the present study, we prepared CacyBP/SIP overexpressing and knockdown cell lines of gastric cancer. Forced CacyBP/SIP expression inhibited the proliferation of gastric cancer cells, suppressed tumorigenicity in vitro, and prolonged the survival time of tumor-bearing nude mice. In addition, increased CacyBP/SIP repressed the invasive potential of gastric cancer cells. Conversely, the down-regulation of CacyBP/SIP by RNA interference showed the opposite effects. Further studies showed that depressed CacyBP/SIP increased the expression of total and nuclear β-catenin at the protein level and elevated the transcriptional activity of Tcf/LEF. Taken together, our results suggest that CacyBP/SIP may be a potential inhibitor of cell growth and invasion in the gastric cancer cell, at least in part through the effect on β-catenin protein expression and transcriptional activation of Tcf/LEF. (Mol Cancer Res 2007;5(12):1254–62)
Algebraic Method for the Analysis of Signaling Crosstalk
Authors: Matsubara Yoshiya , Kikuchi Shinichi , Sugimoto Masahiro , Oka Kotaro , Tomita Masaru
Published: January 2008

A unified mathematical description that expresses the characteristics of whole systems is necessary for an understanding of signal transduction cascades. In this study we explore an algebraic method, named extreme signaling flow, enhanced from the concept of extreme pathway, to analyze signal transduction systems. This method enables us to represent the long-term potentiation (LTP) and the long-term depression (LTD) of hippocampal neuronal plasticity in an integrated simulation model. The model is validated by comparing the results of redundancy, reaction participation, and in silico knockout analysis with biological knowledge available from the literature. The following properties are assumed in these computational analyses: (1) LTP is fault-tolerant under network modification, (2) protein kinase C and MAPK have numerous routes to LTP induction, (3) calcium-calmodulin kinase II has a few routes to LTP induction, and (4) calcineurin has many routes to LTD induction. These results demonstrate that our approach produces an integrated framework for analyzing properties of large-scale systems with complicated signal transduction.
Muscle formation during embryogenesis of the polychaete Ophryotrocha diadema (Dorvilleidae) – new insights into annelid muscle patterns
Authors: Bergter Annette , Brubacher John L , Paululat Achim
Published: January 2008

Background

The standard textbook information that annelid musculature consists of oligochaete-like outer circular and inner longitudinal muscle-layers has recently been called into question by observations of a variety of complex muscle systems in numerous polychaete taxa. To clarify the ancestral muscle arrangement in this taxon, we compared myogenetic patterns during embryogenesis of Ophryotrocha diadema with available data on oligochaete and polychaete myogenesis. This work addresses the conflicting views on the ground pattern of annelids, and adds to our knowledge of the evolution of lophotrochozoan taxa.

Results

Somatic musculature in Ophryotrocha diadema can be classified into the trunk, prostomial/peristomial, and parapodial muscle complexes. The trunk muscles comprise strong bilateral pairs of distinct dorsal and ventral longitudinal strands. The latter are the first to differentiate during myogenesis. They originate within the peristomium and grow posteriorly through the continuous addition of myocytes. Later, the longitudinal muscles also expand anteriorly and form a complex arrangement of prostomial muscles. Four embryonic parapodia differentiate in an anterior-to-posterior progression, significantly contributing to the somatic musculature. Several diagonal and transverse muscles are present dorsally. Some of the latter are situated external to the longitudinal muscles, which implies they are homologous to the circular muscles of oligochaetes. These circular fibers are only weakly developed, and do not appear to form complete muscle circles.

Conclusion

Comparison of embryonic muscle patterns showed distinct similarities between myogenetic processes in Ophryotrocha diadema and those of oligochaete species, which allows us to relate the diverse adult muscle arrangements of these annelid taxa to each other. These findings provide significant clues for the interpretation of evolutionary changes in annelid musculature.
p75 Neurotrophin Receptor Mediates Neuronal Cell Death by Activating GIRK Channels through Phosphatidylinositol 4,5-Bisphosphate
Authors: Coulson Elizabeth J. , May Linda M. , Osborne Shona L. , Reid Kate , Underwood Clare K. , Meunier Frederic A. , Bartlett Perry F. , Sah Pankaj
Published: January 2008

The pan neurotrophin receptor p75NTRsignals programmed cell death both during nervous system development and after neural trauma and disease in the adult. However, the molecular pathways by which death is mediated remain poorly understood. Here, we show that this cell death is initiated by activation of G-protein-coupled inwardly rectifying potassium (GIRK/Kir3) channels and a consequent potassium efflux. Death signals stimulated by neurotrophin-mediated cleavage of p75NTRactivate GIRK channels through the generation and binding of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2/PIP2] to GIRK channels. Both GIRK channel activity and p75NTR-mediated neuronal death are inhibited by sequestration of PtdIns(4,5)P2and application of GIRK channel inhibitors, whereas pertussis toxin treatment has no effect. Thus, p75NTRactivates GIRK channels without the need for Gi/o-proteins. Our results demonstrate a novel mode of activation of GIRK channels, representing an early step in the p75NTR-mediated cell death pathway and suggesting a function for these channels during nervous system development.
Testosterone-Induced Matrix Metalloproteinase Activation Is a Checkpoint for Neuronal Addition to the Adult Songbird Brain
Authors: Kim Dae-Hee , Lilliehook Christina , Roides Breana , Chen Zhuoxun , Chang Mayland , Mobashery Shahriar , Goldman Steven A.
Published: January 2008

Testosterone-induced neuronal addition to the adult songbird vocal control center, HVC, requires the androgenic induction of vascular endothelial growth factor (VEGF), followed by VEGF-stimulated angiogenesis. The expanded vasculature acts as a source of BDNF, which supports the immigration of new neurons from the overlying ventricular zone. In tumorigenesis, a similar process of adult angiogenesis is regulated by matrix metalloproteinase (MMP) activity, in particular that of the gelatinases. We therefore investigated the role of the gelatinases in neuronal addition to the HVC of adult female canaries.In situzymography of the caudal forebrain revealed that testosterone-induced perivascular gelatinase activity that was most prominent in HVC. High-resolution gels revealed distinct MMP activities that comigrated with MMP2 and MMP9, and PCR cloning yielded MMP2 and MMP9 orthologues of 1465 and 1044 bp, respectively. Quantitative PCR revealed that HVC MMP2 mRNA levels doubled within 8 d of testosterone, whereas MMP9 transcript levels were stable. Moreover, isolated adult canary forebrain endothelial cells secreted MMP2, and VEGF substantially increased endothelial MMP2 gelatinase activity. To assess the importance of androgen-regulated, VEGF-induced MMP2 to adult angiogenesis and neurogenesis, we treated testosterone-implanted females with the gelatinase inhibitor SB-3CT.In situzymography confirmed that SB-3CT suppressed gelatinase activity in HVC, and histological analysis revealed that SB-3CT-treated birds exhibited a decreased endothelial mitotic index and substantially diminished neuronal recruitment to HVC. These data suggest that the androgenic induction of endothelial MMP2 is a critical regulator of neuronal addition to the adult HVC, and as such comprises an important regulatory step in adult neurogenesis.
Protein Phosphatase 1-Dependent Bidirectional Synaptic Plasticity Controls Ischemic Recovery in the Adult Brain
Authors: Hédou Gaël F. , Koshibu Kyoko , Farinelli Mélissa , Kilic Ertugrul , Gee Christine E. , Kilic Ulkan , Baumgärtel Karsten , Hermann Dirk M. , Mansuy Isabelle M.
Published: January 2008

Protein kinases and phosphatases can alter the impact of excitotoxicity resulting from ischemia by concurrently modulating apoptotic/survival pathways. Here, we show that protein phosphatase 1 (PP1), known to constrain neuronal signaling and synaptic strength (Mansuy et al., 1998; Morishita et al., 2001), critically regulates neuroprotective pathways in the adult brain. When PP1 is inhibited pharmacologically or genetically, recovery from oxygen/glucose deprivation (OGD)in vitro, or ischemiain vivois impaired. Furthermore,in vitro, inducing LTP shortly before OGD similarly impairs recovery, an effect that correlates with strong PP1 inhibition. Conversely, inducing LTD before OGD elicits full recovery by preserving PP1 activity, an effect that is abolished by PP1 inhibition. The mechanisms of action of PP1 appear to be coupled with several components of apoptotic pathways, in particular ERK1/2 (extracellular signal-regulated kinase 1/2) whose activation is increased by PP1 inhibition bothin vitroandin vivo. Together, these results reveal that the mechanisms of recovery in the adult brain critically involve PP1, and highlight a novel physiological function for long-term potentiation and long-term depression in the control of brain damage and repair.
TEL/AML1+ ACUTE LYMPHOBLASTIC LEUKEMIA IN THE GREEK PEDIATRIC POPULATION
Authors: Papadhimitriou Stefanos , Paterakis Georgios S. , Parcharidou Agapi , Tsakiridou Anastasia , Papadakis Vassilios , Papargyri Sofia , Paissiou Anna , Tourkantoni Natalia , Tsitsikas Konstantinos , Pavlidis Dimitris , Georgiakaki Maria , Polychronopoulou Sophia
Published: January 2008

INTRODUCTION: TEL/AML1+ acute lymphoblastic leukemia (ALL) is considered to be a distinct nosological entity with excellent prognosis, but recent studies have indicated significant clinical heterogeneity.

OBJECTIVE: In this study, we attempted to estimate the incidence and clinical features of TEL/AML1+ ALL for the first time in a representative cohort of Greek pediatric patients.

METHODS: One hundred twenty children (<16 years old) diagnosed with ALL (107 of B-cell origin, 13 of T-cell origin) were screened for TEL/AML1 with interphase fluorescence in situ hybridization by using a commercial probe set. All patients were treated as either standard risk (SR) or high-risk (HR) cases according to a modified BFM-95 (Berlin-Frenkfurt-Munster) protocol. Follow-up ranged between 5 and 87 months (median: 45 months).

RESULTS: Twenty-six patient (all of them will ALL of B-cell origin [24.3%]) were found to be positive for TEL/AML1. The presence of TEL/AML1 was significantly associated with younger age and lower white blood cell count at diagnosis but not with remission duration or overall survival rate. The number of children who relapsed (1 vs 7) or succumbed (1 vs 5) was comparable between the TEL/AML1+ and TEL/AML1− groups of children with ALL of B-cell origin.

CONCLUSIONS: The incidence of TEL/AML1 in Greece seems comparable to that in other European and Mediterranean countries. As in most European studies, the independent prognostic value of TEL/AML1 is in doubt, because it is closely associated with other favorable factors. In this series, the modification of the therapeutic regimen (ie, omission of the SR arm) may be responsible for the similar outcome in TEL/AML1+ and TEL/AML1− cases, because it seems to lower the relapse risk for all children with ALL.