bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTODYNAMIC THERAPY OF NORMAL CEREBRAL TISSUE IN THE CAT: A NONINVASIVE MODEL FOR CEREBROVASCULAR THROMBOSIS
Authors: Chopp Michael , Glasberg Mark R. , Riddle Jeanne M. , Hetzel Fred W. , Welch K. M. A.
Published: January 2008

Abstract The early neuropathological response of normal cat brain to photodynamic therapy was investigated. Photofrin II was injected (IV) into a cat and photoactivated with red light from a filtered incandescent lamp. Animals were subjected to phototherapy either through the intact skull or with energy deposition onto the intact dura. Following photoactivation the animals were maintained for 6 h after which time the brain was removed and sections submitted for electron microscopic and or light microscopic study.

Gross anatomical analysis of the photoactivated brain revealed hemorrhagic dusky discoloration limited to the area of the tissue illuminated. Animals that failed to show a lesion were cats characterized by low Photofrin II dosage and low photoactivation intensity. The microscopic cortical features of cats with lesions included prominent capillary congestion and regions of marked vacuolization and rarefaction. Blood vessels were structurally altered and the lumen of many vessels was completely filled with tightly packed erythrocytes. Our study suggests that the acute neuropathological response of cerebral tissue to photoactivation resembles that of microvascular thrombosis. It is thus reasonable to explore PDT of normal tissue as a non invasive model of cerebrovascular thrombosis in the cat.
PHOTOSENSITIVITY IN THE SKIN OF THE LIZARD, Anolis carolinensis
Authors: Vaughan Gerald L.
Published: January 2008

Abstract Skin of the lizard, Anolis carolinensis, is remarkably sensitive to light. Illuminated in vitro with visible light from a tungsten source (110 W m−2), skin changes from brilliant green to dark brown (50% reduction in reflectance) within 2‐4 min as a result of dispersion of melanin from a perinuclear position within dermal melanophores into superficial dendritic processes. Reversal of the process, reaggregation of pigment, will occur within 2.0 min upon return to darkness. This photic response can be initiated with light levels as low as 5.0 W m−2 and is maximized by light levels only 5% that of midwinter sunshine. Pigment dispersion in response to both melanocyte stimulating hormone and to light is inhibited by cytochalasin‐B, indicating that microfilaments may be the motor element for pigment movement in that direction. Colchicine, but not cytochalasin‐B, totally blocks pigment reaggregation following melanocyte stimulating hormone exposure and partially blocks it in the dark phase of the photic response. The results of this study are consistent with a model for pigment movement in A. carolinensis that provides microfilaments for pigment dispersion and microtubule involvement in both dispersion and aggregation. Finally, because it is readily visible, easily quantified, rapid and reversible, photic response in the skin of A. carolinensis is recommended as a valuable model svstem for the studv of saltatorv movement of oreanelles within cells.
DNA‐PROTEIN CROSSLINKING IN NORMAL HUMAN SKIN FIBROBLASTS EXPOSED TO SOLAR ULTRAVIOLET WAVELENGTHS
Authors: Lai Li‐Wen , Ducore Jonathan M. , Rosenstein Barry S.
Published: January 2008

Abstract Three normal human skin fibroblast cell lines were exposed to the simulated solar UV radiation produced by a fluorescent sunlamp under conditions in which the wavelength components shorter than either 295, 305 or 315 nm were excluded. The level of DNA‐protein crosslinks (DPC) was then measured in those cells using the alkaline elution technique either immediately after irradiation or following a 24 h incubation. In each case, cells were exposed to fluences that induce similar levels of DPC. For cells exposed to 10 kJ m2 of sunlamp UV > 295 nm, the level of DPC exhibited a 2‐5‐fold increase following incubation. In contrast, 40‐100% of the DPC were removed upon incubation of cells irradiated with either 100 kJ m−2 of sunlamp UV > 305 nm or 150 kJ m−2 of sunlamp UV > 315 nm. A major difference between the effects induced by these wavelength regions is that, in addition to DPC, a very high level of pyrimidine dimers is also produced by sunlamp UV > 295 nm, whereas much lower dimer yields result from treatment with either sunlamp UV > 305 nm or sunlamp UV > 315 nm. A potential role for type II DNA topoisomerase in the formation of these DPC resulting from either the change in conformational structure caused by the presence of a high level of dimers or an involvement of this enzyme in dimer excision repair is discussed.
POTENTIAL INVOLVEMENT OF FREE RADICAL REACTIONS IN ULTRAVIOLET LIGHT‐MEDIATED CUTANEOUS DAMAGE*
Authors: Black Homer S.
Published: January 2008

Free radicals are chemical species characterized by an odd number of orbital electrons or by pairs of electrons of similar directional spin isolated singly in separate orbitals. Consequently most of these agents are highly reactive and usually exhibit an extremely short half‐life, although due to steric and resonance effects some exceptions occur. Some radicals and their precursors, such as the diradical O2 which exists in the triplet state, represent a critical and essential element of normal metabolism of aerobic organisms where, under normal circumstances, controlled reduction of reactive oxygen species occurs via the cytochrome oxidase or cytochrome P‐450 mixed function monooxygenase systems. In addition to reactive oxygen species, organisms may be subjected to a wide‐range of other free radicals or their precursors, including those of both exogenous and endogenous origin. Elaborate defense mechanisms have evolved to avoid cellular damage from these highly reactive species. Enzymes, such as the superoxide dismutase, the glutathione peroxidase/reductase system, and catalase; interactions with conjugated diene systems such as those found in melanins, carotenoids, and tocopherols; and direct reduction by sulphydryl compounds, phenols, and purines represent but a few of these natural defense systems.

Despite a strong rationale for considering free radicals as pathologic agents, progress in implicating these agents, or their reactions, in pathologic processes has been arduous. The fore‐most hurdle to providing definitive evidence for free radical involvement rests with the highly transient nature of these species, hardly reaching measurable levels in vivo and thereby making rigorous testing of the hypothesis extremely difficult. Indeed, free radical damage has been studied, for the most part, by indirect means–usually by measurement of known free radical reaction intermediates and products from which free radical involvement is implied. Nevertheless, free radical formation has been shown to occur in UV‐irradiated skin and a considerable body of circumstantial evidence has been amassed that strongly infers that these agents, or reactions initiated by them, are responsible for at least some of the deleterious effects of UV upon skin.
NEAR‐INFRARED DETECTION OF SINGLET MOLECULAR OXYGEN PRODUCED BY PHOTOSENSITIZATION WITH PROMAZINE and CHLORPROMAZINE
Authors: Hall Robert D. , Buettner Garry R. , Moiten Ann G. , Chignell Colin F.
Published: January 2008

A sensitive near‐infrared detection system has been used to study the steady‐state emission of 1O2 at 1268 nra produced by promazine (PZ) and chlorpromazine (CPZ) during photo‐illumination. Singlet molecular oxygen could be detected in a variety of ordinary and perdeuterated organic solvents, but was not detectable in water or deuterium oxide. The emission was enhanced in the perdeuterated organic solvents and could be eliminated by rigorous degassing or by addition of the singlet oxygen scavenger 2,3‐dimethylfuran. Singlet oxygen could not be detected in any of the solvents during irradiation of the sulfoxides of PZ and CPZ. We conclude that in biological systems 1O2 production is not a major pathway to phototoxicity for the sulfoxides, while for the parent phenothiazines the formation of 1O2 is much more likely to be important in nonpolar environments such as cell membranes than in the aqueous parts of the cell.
THE EFFECTS OF ULTRAVIOLET RADIATION EXPOSURE OF ADJACENT CELLS ON PLAQUE FORMATION WITH Herpes simplex VIRUS TYPE I
Authors: Conner Rebecca E. , Babich Michael A. , Coohill Thomas P.
Published: January 2008

African green monkey kidney cells (CV‐1P) were exposed to low fluences of 254 nm germicidal radiation and then infected with Herpes simplex virus, type I. The result of this treatment was an increase in viral plaque development rate, the large plaque effect (LPE). A measurement of the kinetics of plaque development suggested that a large portion of the effect could be due to events occurring in those cells that are adjacent to the initially infected cell. An infectious center assay was employed in order to isolate the effects of ultraviolet radiation (UV) on the initially infected cells from those effects on the adjacent cells that became infected as the plaque spread radially outward. Plaque development began earlier in UV irradiated cells and progressed at a uniformly accelerated rate compared to untreated cells. Results indicate that although the initially infected cell contributes to the LPE, the major effect is due to events that occur in the adjacent cells. Each round of viral replication appears to contribute equally to the LPE. The virally induced rate of fusion of the initially infected cell with its immediate neighbors is not affected by UV.
LIGHT DOSIMETRY FOR PHOTODYNAMIC THERAPY BY WHOLE BLADDER WALL IRRADIATION
Authors: Star Willem M. , Marijnissen Hans P. A. , Jansen Harald , Keijzer Marleen , VAN Gemert Martin J. C.
Published: January 2008

Abstract In Photodynamic Therapy (PDT) there is a need for accurate quantitative light dosimetry. This has become particularly apparent in the treatment of superficial bladder cancer, either by focal or by whole bladder wall irradiation. We have studied this problem using a spherical model of the bladder, consisting of two concentric thin‐walled plastic spheres, 8 and 10 cm in diameter. The inner sphere was filled with water or with a light‐scattering medium. The space between the spheres was filled with an optically tissue equivalent liquid. An isotropic light source was placed at the center of the spheres. Light energy fluence rates (light “dose rates”) during PDT of the bladder simulated in this manner, were measured using a specially developed miniature light detector and were also calculated using a mathematical model. These data were confirmed by measurements in vivo (dog bladder). In the case of focal irradiation at a wavelength of 630 nm, the ratio (R) between the true light fluence rate at the bladder surface and the fluence rate due to the primary light beam is somewhat larger than 1, depending on the diameter of the primary beam. The maximum ratio is 2, for a beam diameter of several centimeters. In the case of whole bladder wall PDT, R is larger than 5. This is due to the strong scattering of (red) light by tissue and indicates that the intensity of the primary beam, which is usually reported, is not a good measure of the true fluence rate for whole bladder wall PDT. When the light source is moved away from the center of the spheres, the rate of change of the fluence rate at the bladder wall is more than a factor of 2 larger when the bladder cavity is filled with a light‐scattering suspension, as compared with water. The use of a light‐scattering medium may therefore not be advantageous to achieve a uniform light distribution across the bladder wall.
THE EFFECT OF PORPHYRIN PHOTOSENSITIZERS ON THE TOXICITY OF l,3‐BIS(2‐CHLOROETHYL)‐1‐ NITROSOUREA IN C57BL/6J MICE
Authors: Muller P. J. , Wilson B. C. , Chada K.
Published: January 2008

Abstract The most widely used agents for photodynamic therapy are the porphyrin photosensitizers. It has been shown that hematoporphyrin derivative (HpD) can cause murine marrow hypercellularity and splenic hypertrophy. We have examined the effect on survival and marrow cellularity of high dose l,3‐bis(2‐chloroethyl)‐l‐nitrosourea (BCNU) after HpD or dihematoporphyrin ether (DHE) pretreatment in C57BL/6J mice.

The lethal toxicity of the LDS0+ 10% dose of BCNU (60 mg kg−1) was significantly reduced by pretreatment with HpD when the HpD was administered at least 3 days prior to the BCNU. HpD administered 1 or 2 days prior to BCNU or after BCNU had no effect. The percent death rate was reduced from 80 to 0% when HpD was administered 7 and 5 days prior to BCNU.

No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg−1 were identified with DHE pretreatment although some increase in median survival was noted in two groups. Some reduction in lethal toxicity was noted when 60 mg kg−1 BCNU was used and the pretreatment dose of DHE was 10 or 25 mg kg−1 given twice 3 days apart. Furthermore, a significant reduction of BCNU induced marrow cell depletion was found when low doses of DHE were used as pretreatment. High doses of DHE resulted in marrow depletion. Both HpD and DHE altered the toxicity of BCNU.

Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs.
PHOTODYNAMIC THERAPY OF HUMAN BLADDER CANCER CELLS in vitro CORRELATED WITH CELLULAR FLUORESCENCE LEVELS OF PHOTOFRIN‐II
Authors: Williams Richard D. , Runge Terrence C.
Published: January 2008

Abstract In order to determine optimum dose of Photofrin‐II (PHI) timing and dose of laser therapy and differential effects of laser on normal and neoplastic human bladder cancer cells in vitro, experiments were carried out using 3 cell lines of human bladder cancer (253‐J, 639‐V, and 647‐V) and a human fibroblast line (CRL‐1507). Cellular Pf‐II uptake and excretion studied using flow cytometric fluorescence analysis of the cells and fluorescence levels of the culture medium showed a wide variability of uptake of Pf‐II among the cell lines. Pf‐II excretion occurred most rapidly in the first 4 h after incubation reaching maximum at 24‐48 h in all cells studied. Cellular concentration of Pf‐II and supernatant levels of Pf‐II estimated by fluorescence levels had a reciprocal correlation. Laser treatment of one cancer line and the fibroblast line at 20 J (630 nm) at various times after incubation with 50 μ.g m−l of Pf‐II showed that the photodynamic effect correlated directly with cellular fluorescence. These results suggest that in vitro: (1) initial uptake of Pf‐II is generally higher in neoplastic than normal cells but that excretion rates are similar; and (2) photodynamic effect is related primarily to initial cellular levels of photosensitizer rather than differential excretion rates.
SOLVENT EFFECTS ON THE ELECTRONIC ABSORPTION AND FLUORESCENCE SPECTRA OF INDOLE‐4‐CARBOXYLIC ACID: PROTOTROPIC EQUILIBRIA IN AQUEOUS SOLUTIONS
Authors: Krishnamurthy Mannam , Mishra Ashok K. , Dogra Sneh K.
Published: January 2008

Abstract— The absorption and fluorescence spectra of indole‐4‐carboxylic acid in various solvents have indicated that the ‐COOH group is more planar with respect to the indole ring in the first excited singlet state (S1) than in the ground (S0) state. Relatively large Stokes' shifts indicate that polarisability and dipole moment of the molecule are increased predominantly upon excitation. Prototropic reactions in the S0 and S1 states are the same. The ‐COO‐ and ‐COOH+2 groups are not coplanar in the S0, but coplanar in the S1 state. pH‐dependent fluorescence spectra have revealed that both protonation and deprotonation of the ‐COOH group increase the basicity of the molecule upon excitation.
COMPARISON OF THE PROTEIN CONFORMATIONS BETWEEN DIFFERENT FORMS (Pr AND Pfr) OF NATIVE (124 kDa) AND DEGRADED (118/114 kDa) PHYTOCHROMES FROM Avena sativa*
Authors: Vierstra Richard D. , Quail Peter H. , Hahn Tae‐Ryong , Song Pill‐Soon
Published: January 2008

Abstract— Circular dichroic properties of native, 124 kDa phytochrome from etiolated Avena sativa seedlings have been examined and compared with those of degraded phytochrome (118/114 kDa). The CD spectrum of the Pr form of 124 kDa phytochrome does not differ significantly in the visible region from that of 118/114 kDa Pr. In contrast, the CD spectrum of the Pfr form of 124 kDa phytochrome differs from that of the 118/114 kDa species in the far‐red, red and blue regions of the spectrum. This result confirms that the NH2‐terminal polypeptide segment has a critical role in chromophore‐protein interaction in the Pfr but not in the Pr form. In the UV region, 124 kDa phytochrome exhibits a photoreversible difference between the CD spectra of Pr and Pfr, whereas no such difference is observed for 118/114 kDa preparations. These data suggest a possible photoreversible change in secondary structure of the 124 kDa phytochrome polypeptide that requires the presence of the 6/10 kDa NH2‐terminal domain to occur.
2,7‐DIIODO‐9‐DIAZOFLUORENE: A POTENTIAL REAGENT FOR PHOTOLABELING
Authors: Rak Stanton F. , Schuster Gary B.
Published: January 2008

Abstract— The photochemistry of 2,7‐diiodo‐9‐diazofiuorene was studied to examine its suitability as a photolabeling agent of hydrophobic sites in biological assemblies. Irradiation of the diazo compound generates 2,7‐diiodofluorenylidene. The carbene was detected by laser transient absorption spectroscopy and characterized by its chemical and physical properties. Like fluorenylidene, the triplet is the ground state of 2,7‐diiodofluorenylidene. However, the substituted triplet carbene does not reform its higher energy, electrophilic singlet state fast enough for reactions of the upper state to compete with the irreversible consumption of the triplet. Thus, the products from the reactions of diiodofluorenylidene contain a higher proportion of those characteristic of the triplet carbene than occurs in the reactions of fluorenylidene. This will limit the utility of this diazocompound as a photolabeling agent.
INVARIANT PROPERTIES OF ABSORPTION PROFILES IN SPORANGIOPHORES OF Phycomyces blakesleeanus UNDER BALANCING BILATERAL ILLUMINATION
Authors: Steinhardt A. R. , Jr W. Shropshire , Fukshansky L.
Published: January 2008

Abstract— Absorption spectra and spectra of the refractive indices were separately measured for cytoplasm and vacuole of Phycomyces blakesleeanus in the wavelengths domains 300 to 750 nm and 250 to 750 nm respectively. These data were then used to simulate absorption profiles for different orientations of the photoreceptor for measured action spectra for phototropic balance. The photoreceptor was assumed to be a flavin. Using the reference wavelengths 394, 450 and 507 nm as an example it is shown that the absorption profiles have, independent of the photoreceptor orientation, invariant properties. Under bilateral balancing illumination the symmetry of the absorption profiles is conserved and the total amount of energy absorbed at proximal and distal sides is an invariant under a symmetry transformation front to the rear side.
WAVELENGTH‐DEPENDENT QUANTUM YIELD OF OH RADICAL FORMATION FROM PHOTOLYSIS OF NITRITE ION IN WATER
Authors: Zafiriou Oliver C. , Bonneau Roland
Published: January 2008

Abstract. Photolysis (298<ambda;<371 nm) of aqueous solutions of nitrite ion near neutral pH yields the hydroxyl radical. Its wavelength‐dependent quantum yield lies in the range 0.015‐0.08, as determined by Br‐ or SCN‐ scavenging of OH and 3BP (benzophenone) actinometry. The significance of these results, and their dependence on pH, temperature, and [O2], for the photolysis of nitrite in seawater is discussed briefly.
SOLVENT EFFECTS ON THE PHOTOPHYSICAL PROPERTIES OF DIBUCAINE: A QUINOLINE ANALOGUE
Authors: Lin C. T. , Malak M. , Vanderkooi G. , Mason W. R.
Published: January 2008

Abstract— Emission and absorption spectra of neutral, monocation and dication dibucaine were recorded in hydrocarbon and hydroxylic solvents. The spectral analysis indicates that the lowest electronic states of dibucaine originate from the quinoline analogue in the molecule. The fluorescence and phosphorescence emission of neutral dibucaine in all solvents at 77 K are best assigned as resulting from 1n,π* and 3π,π*, respectively, whereas those of both monocation and dication dibucaines are found to have 1π,π* and 3π,π*. The monocation and neutral dibucaines in ethanol solutions were shown to give identical emission spectral properties, indicating that dibucaine‐HCl in ethanol is H+ dissociative; this was confirmed by FT‐IR studies. The possible explanations for the deprotonation of dibucaine‐HCl in ethanol environments are discussed.
PHOTOREACTION OF PSORALEN DERIVATIVES WITH STRUCTURALLY ORGANIZED DNA
Authors: Gia O. , Palu G. , Palumbo M. , Antonello C. , Magno S. Marciani
Published: January 2008

Abstract— The DNA‐photobinding process of a number of psoralen derivatives has been investigated using different nucleic acid structures, such as double helical DNA, nucleosomes, and chromatin under various ionic strength conditions. Important differences were observed using “free”vs organised DNA as the target macromolecule, which are related to conformational, stereochemical, ionic and competition effects. The furocoumarin chemical nature also plays a role; in particular, charged compounds are shown to be more reactive than uncharged analogues with free DNA at low salt concentration, whereas a levelling off in photobinding efficiency occurs on increasing ionic strength and nucleic acid complexity. These results allow an explanation for the photobiological effects of the examined psoralens.
AN INSTRUMENT FOR SIMULTANEOUS ACQUISITION OF FLUORESCENCE SPECTRA AND FLUORESCENCE LIFETIMES FROM SINGLE CELLS
Authors: Ramponi Roberta , Rodgers Michael A. J.
Published: January 2008

Abstract— An instrument is described that has the capability of acquiring both the spectrum and lifetime(s) of fluorescent species dispersed in biological cells. It operates at the single cell (or organelle) level and the spectral and temporal data collection can be performed simultaneously. A synchronously pumped, mode‐locked dye laser provides the excitation light, time‐correlated single‐photon counting is used for lifetime measurements, and a diode array spectrograph is used for spectral work. Spatial resolution of sub‐micrometer is obtained using a fluorescence microscope. The temporal resolution is better than 300 ps and wavelength resolution is less than 1 nm per channel. The instrument has been used for observing the spectral and temporal characteristics of hematoporphyrin in mouse myeloma cells.
STUDIES OF SODIUM TAUROCHOLATE MICELLES USING FLUORESCENT PROBE MOLECULES
Authors: Nithipatikom Kasem , McGown Linda B.
Published: January 2008

AbstractMicelles formed by sodium taurocholate (NaTC) and mixed micelles formed by NaTC with detergents (SDS, reduced Triton X‐100 and CTAC) were studied with fluorescent probes. Pyrene was used as an indicator of the polarity of the micellar binding site by comparison of the fluorescence spectra and vibronic band intensity ratios of pyrene in the different systems. Perylene was used as a fluorescence polarization probe to study the rigidity of the NaTC and mixed micelles. The fluorescence lifetime of perylene in the different systems was also measured. Results of the studies were compared with measurements of the probes in cyclohexane, ethanol and aqueous beta‐cyclodextrin. Perylene was found to be more rigidly bound in the NaTC micelles than in the detergent micelles. Insertion of small amounts of reduced Triton X‐100 into the NaTC micelles appears to increase the rigidity. The binding sites of NaTC and CTAC have similar polarities, and are more polar than those of SDS and reduced Triton X‐100. Insertion of any of the detergents into the NaTC micelle decreases the polarity of the binding site, possibly by reducing the penetration of water into the micelle.
HERBICIDE MEDIATED UV‐RESISTANCE IN CYANOBACTERIA: ON THE ROLE OF PHOTOSYNTHETIC ELECTRON TRANSPORT SYSTEM RATHER THAN REPLICATIVE DNA AS LETHAL TARGET DETERMINING DARK‐SURVIVAL OF Anacystis nidulans
Authors: David K. A. V. , Rane S. S. , Mathur Manjula , Bhattacharjee S. K.
Published: January 2008

Abstract— The role of the replicative state of DNA and of the photosynthetic electron transport system in determining UV‐sensitivity of A. nidulans under conditions of non‐photoreactivation (by incubating the cells for 24 h in the dark following UV‐irradiation) has been investigated. Both the DNA synthesis data and the data on survival levels during cell cycle synchrony forced by light to dark and dark to light transitions showed that the differential UV‐sensitivity was not correlated with the replicative state of the DNA as suggested earlier. However, incubation in the light with the herbicides 2/3‐4, dichlorophenyl/‐l, 1‐dimethyl urea (DCMU) and 2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine (atrazine) which are known to inhibit electron transport by specifically binding to the high turnover B protein of photosynthetic electron transport system II (PSII), enhanced the UV‐resistance with kinetics similar to those of a culture transferred from light to dark. We interpret this result as implicative of PSII as the second lethal target in the case of cyanobacteria. The inactivation of electron transport activity of PSII as measured by the fall in DCMU‐sensitive fluorescence yield during post‐UV dark incubation supports this hypothesis. It is proposed that in wild type cells the survival under conditions of non‐photoreactivation following UV‐irradiation is essentially determined by the level of dark‐repair of damage to PSII and that the 32 kD B protein may have a role in dark‐repair of damage to the electron transport system. This hypothesis explains the paradox of negative liquid holding recovery phenomenon under conditions which promote excision‐repair of damaged DNA in cyanobacteria.
DELAYED PLATING RECOVERY OF DIPLOID YEAST EXPOSED TO ULTRAVIOLET LIGHT BETWEEN 254 AND 313 nm WAVELENGTH
Authors: Schall Monika , Kiefer Jüjrgen
Published: January 2008

Abstract— Diploid yeast cells exposed to UV‐light of different wavelengths in the region between 254 and 313 nm were assessed for their ability of delayed plating recovery. They were either held in non‐nutrient suspension (‘liquid holding’) or on non‐nutrient agar before final plating. Thus it was possible to distinguish between real and apparent recovery due to cell multiplication. The experiments showed that no delayed plating recovery was found beyond 295 nm wavelength UV.
PHOSPHORESCENCE FROM 2‐(p‐TOLUIDINYL)NAPHTHALENE‐6‐SULFONATE AND l‐ANILINONAPHTHALENE‐8‐SULFONATE, COMMONLY USED FLUORESCENCE PROBES OF BIOLOGICAL STRUCTURES
Authors: MANIARA G. , VANDERKOOI J. M. , BLOOMGARDEN D. C. , KOLOCZEK H.
Published: January 2008

Abstract— Phosphorescence at room temperature was observed for the 2‐(p‐toluidinyl)naphthalene‐6‐sulfonate (TNS) and l‐anilinonaphthalene‐8‐sulfonate (ANS) bovine serum albumin complexes. It is suggested that the phosphorescence lifetimes of a few milliseconds for TNS and ANS will allow for the study of processes occurring on this time scale in biological macromolecules.
HIGH LEVELS OF 4,5′,8‐TRIMETHYLPSORALEN PHOTOINDUCED FURAN‐SIDE MONOADDUCTS CAN BLOCK CROSS‐LINK REMOVAL IN NORMAL HUMAN CELLS
Authors: Papadopoulo D. , Averback D. , Moustacchi E.
Published: January 2008

Abstract— The induction and removal of DNA interstrand cross‐links (CL) was studied in normal human fibroblasts (1BR/3) using the highly photoreactive furocoumarin 4,5′,8‐trimethylpsoralen (TMP) in combination with monochromatic 365 nm and/or 405 nm radiation. We report that the presence of large amount of furan‐side monoadducts (MAf) induced by TMP plus 365 nm radiation blocks CL incision. When the amount of MAf is reduced by their conversion into even more CL, incision of the cross‐links is more efficient.
THE FLUORESCENCE PROPERTIES OF ORTHO AMINOBENZOATE ANESTHETICS IN DEFINED SOLVENTS AND PHOSPHOLIPID VESICLES
Authors: Birmachu Woubalem , Reed Juta K.
Published: January 2008

Abstract— The fluorescence properties of three ortho aminobenzoate local anesthetics have been determined in a variety of solvents. Results from these studies have been used to deduce how these drugs interact with phosphatidylcholine bilayers. The emission energy, fluorescence quantum yield and lifetime exhibited a biphasic dependence on solvent polarity. In aprotic solvents, alcohols and in ethanol‐water mixtures containing less than 40% water, quantum yields and lifetimes were high (approximately 0.55 and 8.5 ns respectively). In ethanol‐water mixtures containing >40% water, the strong fluorescence quenching was primarily due to an increase in the rate of non‐radiative deactivation of the excited state. Both the radiative (kr) and non‐radiative (knr) rate constants show a biphasic dependence on solvent polarity. These studies suggest the presence of two singlet excited states for these molecules, a polar singlet excited state, S1‐p and a charge transfer excited state, S1‐ct with the latter predominating in ethanol‐water mixture containing >40% water. In egg phosphatidylcholine bilayers, the fluorescence, lifetime and quantum yield are consistent with the view that these drugs are localized within the lipid head group region where the charge‐transfer excited state can be stabilized by intermolecular hydrogen bonding.
IMPAIRMENT OF RED CELL MEMBRANE CYTOSKELETON BY PROTOPORPHYRIN‐IX: LIGHT AND DARK EFFECTS
Authors: Dadosh N. , Shaklai N.
Published: January 2008

Abstract— Membrane cytoskeletons were separated by use of TritonX–100 from freshly isolated red cells, fixed with glutaraldehyde and their morphology was followed by scanning electron microscopy. At 37°C and pH 6.5 cytoskeletons retained cell‐like shapes for at least 2 h, but at higher pH values, they lost stability after 30 min, appearing as amorphous protein material. Irradiation in the presence of1–20 μM protoporphyrin‐IX at pH 6.5 caused crosslinking of the proteins when organized as cytoskeletons, but not when separated. Scanning electron microscopy also revealed that the cytoskeletal proteins conserved their cell‐like shape even at pH values higher than 7.0. It was concluded that illumination in the presence of porphyrin causes membrane rigidity by crosslinking of the cytoskeletal proteins, and their sensitivity to crosslinking is the result of their mutual arrangement in the membrane. At concentrations higher than 100 μM protoporphyrin‐IX induced, even in the absence of light, the opposite effect, namely dissociation of the cytoskeletal proteins. The data suggest that the changes observed in this study provide an explanation for both dark and light induced injuries of red cells in porphyria disorders.
COMPARISON OF FREE RADICALS PRODUCED BY LASER AND ULTRASOUND ABLATION OF CARDIOVASCULAR TISSUE
Authors: Clarke R. H. , Nakagawa K. , Isner J. M.
Published: January 2008

Abstract— We have used the method of spin trapping and EPR to study the nature of the free radicals produced by laser photoreaction of cardiovascular tissue. The results obtained with argon‐ion (cw) and excimer (pulsed) lasers have been compared with radicals produced by ultrasonic disruption of the tissue samples. These comparative studies provide an understanding of the mechanism by which laser light energy effects photoablation of cardiovascular tissue in the pulsed vs cw mode of operation.
A MORE EXACT THEORETICAL INTERPRETATION OF RECENT EXPERIMENTAL DATA OBTAINED USING THE SEPARATED SENSITIZER AND SUBSTRATE METHOD TO INVESTIGATE O2(lδg) INTERACTIONS. POSSIBLE IMPORTANCE OF O2(1σg+)
Authors: Parker J. G.
Published: January 2008

Abstract— Recent experimental data obtained using the separated sensitizer and substrate method to investigate the interaction of O2(1δg) with various substances has been re‐interpreted by means of a more complete theory. Comparison of experimental and recalculated values of the dependence of relative reaction rates on the sensitizer‐substrate separation indicate general accord for experiments in which singlet oxygen acceptors in aqueous solution were used. The presumption is therefore that singlet molecular oxygen O2(1δg) is indeed the active oxidizing agent and that the theory presented and experiment are entirely in agreement.

For experiments in which bacterial targets were used a very distinct disagreement between theory and experiment is evident, the conclusion being that the kill rate does not depend linearly on the O2(1δg) concentration in the immediate proximity of the bacteria. However, the data is consistent with a quadratic dependence on the 1δg concentration. A possible conclusion therefore is that the cytotoxic species is actually O2(1σ+g), formed by an energy pooling reaction involving two O2(1δg) molecules.
INDUCTION OF DNA‐PROTEIN CROSS‐LINKS IN CHINESE HAMSTER CELLS BY THE PHOTODYNAMIC ACTION OF CHLOROALUMINUM PHTHALOCYANINE AND VISIBLE LIGHT
Authors: Ramakrishnan Narayani , Clay Marian E. , Xue Liang‐YAN , Evans Helen H. , Rodriguez‐Antunez Antonio , Oleinick Nancy L.
Published: January 2008

Abstract— Chloroaluminum phthalocyanine (CAPC) is an efficient photosensitizer for the inactivation of Chinese hamster V79 cells. In order to investigate possible molecular mechanisms in the photo‐dynamic action of CAPC and visible light, the induction and repair rate of two classes of DNA lesions have been determined, i.e. DNA single‐strand breaks and DNA‐protein cross‐links. In cells pretreated with 1 μ.M CAPC, a fluence of 12 kJ/m2 of red light (>600 nm) kills approximately 50% of the cells and induces 3 to 3.5 Gy‐equivalents of single‐strand breaks. The repair of these breaks was slower than the repair of single‐strand breaks induced by m̀‐irradiation. The photodynamic action of CAPC also induces a large number of DNA‐protein cross‐links which, in contrast to m̀‐radiation‐induced DNA‐protein cross‐links, do not appear to be repaired during 4 h of post‐treatment incubation in fresh medium. These studies suggest that DNA may be an important target for the cytotoxicity of CAPC + red light.
DETERMINATION OF THE ACRYLAMIDE QUENCHING CONSTANT FOR PROTEIN AND MODEL INDOLE TRIPLETS
Authors: Ghiron Camillo , Bazin Marc , Santus Rene
Published: January 2008

Abstract— The decay of the indole triplet of single tryptophan‐containing proteins and model compounds can be readily measured at room temperature in aqueous solution by monitoring the triplet‐triplet absorption or phosphorescence emission following a 265 nm exciting laser pulse. The quenching action of acrylamide on the triplet excited state of indole side chains was studied in an analogous fashion to that previously done at the singlet level (Eftink and Ghiron, 1977). The acrylamide triplet quenching constant (tkq) ranged from a high of 7.8 times 108M‐1 s‐1 for the exterior indole of corticotropin (ACTH) to a low of 2 times 105 Af‐1 s‐1 for the interior indole of ribonuclease T, (RNase T,). The ratio (7) of these values with their respective acrylamide singlet quenching constants (tkq),(γ=tkq8Kq) ranged from a high of 0.22 for ACTH to a low of 0.001 for RNase T1,. Acrylamide is also an inefficient quencher of model indoles in various solvents (i.e. it has a γ less than 1). The magnitude of γ varied from a high of 0.3 in H20 to a low of 0.02 in acetonitrile, but did not correlate with viscosity, dielectric constant or polarity. The lower efficiency observed for internal indole groups can not be explained by that class of models which predict the presence of static quenching at the triplet level, since none was observed. The present results confirm the observation of Calhoun et al. of a large discrepancy between acrylamide's singlet and triplet quenching constants for buried indole side chains, but suggest that it may be largely explained by the fact that acrylamide is an inefficient quencher of the indole triplet state (1983). The magnitude of this inefficiency is probably determined by specific microenvironmental factors. Thus, unlike 8Kq, the environmentally sensitive lkH cannot be easily used to characterize the dynamics of proteins.
BOOK REVIEW
Authors: Song Pill‐Soon
Published: January 2008

Biophysical Studies of Retinal Proteins. Edited by Thomas G. Ebrey, Hans Frauenfelder, Barry Honig, and Koji Nakanishi.
TRANSIENT INTERMEDIATES IN INTRAMOLECULARLY PHOTOSENSITIZED PYRIMIDINE DIMER SPLITTING BY INDOLE DERIVATIVES
Authors: Young Tish , Kim Sang‐Tae , Van Camp John R. , Hartman Rosemarie F. , Rose Seth D.
Published: January 2008

Abstract— Intramolecularly photosensitized pyrimidine dimer splitting can serve as a model for some aspects of the monomerization of dimers in the enzyme‐substrate complex composed of a photolyase and UV‐damaged DNA. We studied compounds in which a pyrimidine dimer was covalently linked either to indole or to 5‐methoxyindole. Laser flash photolysis studies revealed that the normally observed photoejection of electrons from the indole or the 5‐methoxyindole to solvent was diminished by an order of magnitude for indoles with dimer attached (dimer‐indole and dimer‐methoxyindole). The fluorescence lifetime of dimer‐indole in aqueous methanol was 0.85 ns, whereas that of the corresponding indole without attached dimer (tryptophol) was 9.7 ns. Similar results were obtained for the dimer‐methoxyindole (0.53 ns) and 5‐methoxytryptophol (4.6 ns). The quantum yield of dimer splitting for the dimer‐methoxyindole (φ287K7 = 0.08) was only slightly greater than the value found earlier for the dimer bearing the unsubstituted indole (4>2K7= 0.04). Transient absorption spectroscopy also revealed lower yields of indole radical cations following laser flash photolysis of dimer‐indole compared to the indole without attached dimer. Dimer‐methoxyindole behaved similarly. These results are interpreted in terms of an enhanced rate of radiationless relaxation of the indole and methoxyindole excited singlet states in dimer‐indoles. The possible quenching of the indole and methoxyindole excited states via electron abstraction by the covalently linked dimer is discussed.
ON THE DNA BENDING BY PSORALEN INTERSTRAND CROSSLINKING. A GEL ELECTROPHORETIC STUDY
Authors: Zhen Wei‐Ping , Dahl Otto , Buchardt Ole , Nielsen Peter E.
Published: January 2008

Abstract— A synthetic, partially double stranded decadeoxyribonucleotide with cohesive ends, containing one potential psoralen photo‐crosslinking site centrally positioned (5′‐d(CGGGCTACCC) + 3′‐d(CCGATGGGGC)), has been ligated to double stranded DNA oligomers, which were subsequently photoreacted with 4,5′,8‐trimethylpsoralen. It was found that psoralen DNA interstrand crosslinking does not significantly alter the electrophoretic mobility of these DNA molecules in polyacrylamide gels. Based on this, we conclude that any bends in the DNA helix that may be induced by psoralen DNA interstrand crosslinking must be significantly less than the 45° proposed by Tomic et at. (1987) (Science, 238, 1722) and/or of a different nature than the DNA sequence dependent bends due to d(A)n tracts.
MODE OF COACTION BETWEEN UV‐A AND LIGHT ABSORBED BY PHYTOCHROME IN CONTROL OF APPEARANCE OF RIBULOSE‐1.5‐BISPHOSPHATE CARBOXYLASE IN THE SHOOT OF MILO (Sorghum vulgare Pers.)
Authors: Drumm‐Herrel Helga , Mohr Hans
Published: January 2008

Abstract— In shoots of milo (Sorghum vulgare Pers.) appearance of ribulosebisphosphate carboxylase (RuBPCase) and of translatable mRNA for its small subunit is stimulated strongly by red light (R, operating through phytochrome) and UV‐A light (UV‐A). Ultraviolet‐A is more effective than R.

The mode of coaction between phytochrome and light absorbed by the blue/UV‐A light photoreceptor (‘cryptochrome’) was analyzed in detail in case of enzyme appearance. Fluence rate dependencies, lagphases and the time course of the response are compatible with the view that UV‐A intensifies a process which is occurring in R alone albeit at a lower rate.

With both light qualities the light effect is fully reversible by far‐red light up to 1 h. This means that during this period only phytochrome (Pfr) controls the terminal response, i.e. the actual appearance of RuBPCase. During this 1 h period after the onset of light UV‐A or R have no effect on the level of translatable mRNA for the small subunit of RuBPCase indicating that it requires more than 1 h for the light signal to affect gene expression.

When R and UV‐A are given longer onset of escape from full reversibility is observed at the same time for both light qualities in the case of RuBPCase appearance. The extent of the reversible response is greater after UV‐A pretreatment than after a R pretreatment.

It is argued that the data are consistent with the concept that phytochrome (Pfr) controls the terminal photoresponse, in the present case appearance of RuBPCase, while light absorbed via cryptochrome leads to an increase in responsiveness of the RuBPCase producing machinery towards Pfr.
IMPORTANCE OF NEIGHBORING GROUP PARTICIPATION IN THE REMARKABLY RAPID PHOTOREDUCTION OF 1,1,4,4‐TETRAMETHYL‐l,4‐DIHYDRO‐2,3‐NAPHTHALENEDIONE#
Authors: Scaiano J.C. , Wintgens V. , Netto‐Ferreira J.C.
Published: January 2008

Abstract— The photochemistry of 1,1,4,4‐tetramethyl‐1,4‐dihydro‐2,3‐naphthalenedione (I) in the presence of hydrogen donors has been examined in solution at room temperature by laser flash photolysis. The triplet state of I shows a remarkable reactivity towards hydrogen abstraction, exceeding that of biacetyl by ca. three orders of magnitude, and being comparable, and occasionally exceeding that of triplet benzophenone. This remarkable behavior is attributed to a considerable degree of stabilization of the transition state due to intramolecular hydrogen bonding.
MINIATURE PIG AS AN ANIMAL MODEL TO STUDY PHOTOAGING*
Authors: Fourtanier A. , Berrebi C.
Published: January 2008

Abstract— Seven miniature pigs were irradiated thrice weekly over a 14 months period with suberythem‐atogenic doses of UVB and UVA. Another seven were not exposed, to record innate aging changes.

Chronic irradiation induced the following changes: 1. Increased scaling, with thickening of the stratum corneum and decreased reactivity to acetic acid. 2. Increased minimum erythema dose, corresponding to decreased transmission of UV‐radiation through isolated epidermis. 3. Increased elastic fibers, accompanied by strong deposition of glycosaminoglycans in the upper dermis. 4. Increased laxity with greater extensibility to a deforming torque. 5. Increased density of vessels. 6. More disorderly arrangement of collagen bundles with minor alterations in collagen biochemistry.

These changes mimic those in photoaged human skin but are milder in degree, attributable to the low total dosage of ultraviolet radiation.
PHOTOPRODUCTION OF HYDROGEN FROM LINKED CHROMOPHORES
Authors: CREASER I. I. , HAMMERSHØI A. , LAUNIKONIS A. , MAU A. W.‐H. , SARGESON A. M. , SASSE W. H. F.
Published: January 2008

Abstract On irradiation of solutions of anthryl‐substituted cobalt(III) cage complexes, [(l‐(anthryl‐9‐methylamino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane) cobalt(III)]3+ or [(l‐(4‐an‐thryl‐9)‐3‐aza‐butyl‐l‐amino)‐8‐methyl‐3,6,10,13,16,19‐hexaazabicyclo [6.6.6] eicosane)cobalt (III)]3* in the presence of ethylenediaminetetraacetic acid and platinum catalysts hydrogen was produced. These complexes act as coupled photosensitizers (anthracene moiety) and electron relays (cobalt cage) to produce H2via energy trapping and intramolecular electron transfer initially. The intensity of fluorescence and the photochemical reactivity favour the latter complex and the excited singlet state of the anthracene chromophore is invoked as the intermediate state leading to the reduction of Co(III) to Co(II).
THE PHOTODYNAMIC EFFECTS OF PHOTOFRIN II, HEMATOPORPHYRIN DERIVATIVE, HEMATOPORPHYRIN, AND TETRASODIUM‐MESO‐TETRA(4‐SULFONATOPHENYL)PORPHINE in vitro:
Authors: WEST CATHARINE M. L. , MOORE JAMES V.
Published: January 2008

Abstract The human colon adenocarcinoma cell line, WiDr, was exposed to Photofrin II, hemato‐porphyrin derivative (HPD), hematoporphyrin (HP) or tetrasodium‐meso‐tetra(4‐sulfonatophenyl)‐porphine (TPPS4) followed by irradiation with light. Clonogenicity was determined and the resultant survival curves compared and shown to be qualitatively similar in shape. However, for equal amounts of drug in the medium, there were large differences in photosensitizing efficiency with Photofrin II approximately 5, 25 and 50 fold more effective than HPD. HP and TPPS4, respectively. For the same power used, all drugs were less efficient photosensitizers under red light (600–1100 nm) than under white light (300–1100 nm). For all drugs this could be explained in terms of changes in light absorption over the two wavelength ranges. Differences in clonogenic cell survival could not be explained in terms of differences in singlet oxygen production (from published values). A reduction in drug uptake into the cells was sufficient to explain the differences between Photofrin II, HPD and HP. while TPPS4 was 5‐fold less effective compared to other drugs than would be expected from drug uptake measurements. Two methods for measuring drug uptake were compared and shown to give different results for Photofrin II. Measurement of drug fluorescence in 0.1 N NaOH yielded 5‐fold lower values than when measurements were in 1 N HCl following heat treatment to monomerise aggregated drug. Clearly the reliability of the method used in determining drug uptake must be carefully ascertained.
BOOK REVIEW
Authors: SUTHERLAND BETSY M.
Published: January 2008

DNA Repair: A Laboratory Manual of Research Procedures, Volume 3.
RESISTANCE OF HUMAN and MOUSE MYELOID LEUKEMIA CELLS TO UV RADIATION
Authors: Poljak‐Blazi Marija , Osmak Maja , Hadzija M.
Published: January 2008

Abstract—

Sensitivity of mouse bone marrow and myeloid leukemia cells as well as the sensitivity of human myeloid leukemia cells to UV light was tested. Criteria were the in vivo colony‐forming ability of UV exposed cells and the inhibition of DNA synthesis during post‐irradiation incubation for 24 h in vitro. Mouse bone marrow cells irradiated with a small dose of UV light (5 J/m2) and injected into x‐irradiated animals did not form hemopoietic colonies on the recipients' spleens, and the recipients died. However, mouse leukemia cells, after irradiation with higher doses of UV light, retained the ability to form colonies on the spleens, and all recipient mice died with typical symptoms of leukemia. In vitro, mouse bone marrow cells exhibited high sensitivity to UV light as compared to mouse myeloid leukemia cells. Human leukemia cells were also resistant to UV light, but more sensitive than mouse leukemia cells. These results indicate that myeloid leukemia cells are resistant to UV light as compared with normal bone marrow cells.