bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF SOLAR AND ARTIFICIAL UV IRRADIATION ON MOTILITY AND PHOTOTAXIS IN THE FLAGELLATE, Euglena gracilis
Authors: Hauder Donat‐P. 
Published: January 2008

AbstractThe effect of solar irradiation on the percentage of motile cells, their average speed and their phototactic orientation to white actinic light was studied in the flagellate, Euglena gracilis. Unfiltered solar radiation in midsummer during mid‐day at a location near Lisboa, Portugal, was found to impair motility within 2 h. This effect is exclusively due to the UV‐B component of the radiation and not due to UV‐A, visible light or a temperature increase. Likewise, phototactic orientation was drastically impaired. Reduction of the solar UV‐B irradiation by insertion of an ozone‐Hooded plexiglass cuvette partially reduced the inhibition and covering the cuvettes with glass prevented any decrease in motility and photoorientation. Similar results were found with artificial irradiation (Xe lamps). After inoculation the motility of the population follows an optimum curve (optimum at 8 days). Also, the UV‐B effect on motility was smallest after about one week and increased for younger and older cultures.
OXIDATION OF WATER WITH PHOTOCATALYST—I. REDUCTION OF ELECTRON ACCEPTORS IN WATER SOLUTION WITHOUT ADDITIONAL ELECTRON DONORS
Authors: Marinov Beniamin S. 
Published: January 2008

AbstractPhotoreduction of electron acceptors—myoglobin, hemin and methyl viologen—sensitized by eosin or methylene blue in water solution was studied. The rate of photoreduction of acceptors grows with increasing pH. At pH 9.0 quantum yield of myoglobin reduction reached 1.5%, whereas the efficiency of the low molecular weight acceptors—hemin and methyl viologen—was much lower. Control experiments demonstrated that buffer molecules and the protein moiety were not the source of electrons for the reduction. All the data support the conclusion that in the process under the study hydroxide ions of water appear to be the linal electron donors.
PHOTOCLEAVAGE OF DNA IN THE PRESENCE OF SYNTHETIC WATER‐SOLUBLE PORPHYRINS
Authors: Praseuth Dani`le , Gaudemer Alain , Verlhac Jean‐Baptiste , Kraljic I. , Sissoëff I. , Guillé E. 
Published: January 2008

AbstractIn the presence of oxygen and visible light, various synthetic water‐soluble porphyrins cleave pBR 322 plasmid supercoiled DNA (form I) producing relaxed (form II) and linear (form III) DNA corresponding to single‐strand and double‐strand breaks respectively. Large variations are observed in the efficiency of the porphyrins containing a diamagnetic metal or no metal at all. Singlet oxygen (1O2) seems to be involved in the mechanism of cleavage consistent with the inhibitory effect of the azide anion, N–3. The higher efficiency of cationic porphyrins (as compared to anionic ones) is due to their greater affinity for DNA as shown by experiments carried out at either high ionic strength or in the presence of the surfactant, sodium dodecyl sulfate.
ULTRAVIOLET HYPERSENSITIVITY OF COCKAYNE SYNDROME LYMPHOBLASTOID LINES—THE EFFECTS OF EXOGENOUS β‐NICOTINAMIDE ADENINE DINUCLEOTIDE
Authors: Otsuka Fujio , Kukita Atsushi 
Published: January 2008

AbstractFour Cockayne Syndrome (CS) lymphoblastoid lines were tested for the lethal effects of UV radiation (254 nm) with or without addition of exogenous β‐nicotinamide adenine dinucleotide (β‐NAD +) to their culture medium. Two of them exhibited a small but significantly increased resistance to UV radiation when β‐NAD+ was added to the culture. However, their UV sensitivity after β‐NAD + addition was still much greater than that of normal control lines. Normal control lymphoblastoid lines and those from complementation group A and group C of xeroderma pigmentosum (XP) did not reveal any differences in post‐UV sensitivity after the addition of exogenous β‐NAD+. Thus the abnormal response to the lethal effects of UV radiation of CS lymphoblastoid lines could not be rectified by β‐NAD+ addition. However, β‐NAD+ does appear to play some partial role in reducing the high UV sensitivity of some CS lymphoblastoid lines.
ELIMINATION OF RESIDUAL TUMOR CELLS FROM AUTOLOGOUS BONE MARROW GRAFTS BY DYE‐MEDIATED PHOTOLYSIS: PRECLINICAL DATA*
Authors: Sieber Fritz 
Published: January 2008

Abstract MC540‐mediated photolysis has several features that make it potentially attractive as a clinical purging procedure. (1) The experience with experimental tumors suggests that MC 540‐mediated photolysis is effective against a broad range of leukemias and solid tumors, including drug‐resistant tumors (Sieber et al., 1984b). Drug‐resistant tumor cells are likely to occur in heavily pretreated patients. (2) MC540‐mediated photolysis is not cell‐cycle dependent (Manna and Sieber, 1985). It kills both resting and cycling cells. In this regard, MC 540‐mediated photolysis is a valuable complement to cell‐cycle specific cytotoxic drugs. (3) There is a large differential in sensitivity between normal pluripotent hematopoietic stem cells and leukemia and neuroblastoma cells. (4) The mechanism of action of MC 540‐mediated photolysis is different from that of lectins, antibodies and most cytotoxic drugs. MC 540 binds to the lipid portion of the plasma membrane and membrane lipids are probably a primary target of the toxic photoproducts. Antibodies and lectins react with proteins and carbohydrates and most drugs have intracellular targets (e.g. nuclear DNA). We would therefore expect little cross‐resistance if MC 540‐mediated photolysis were used in combination with other purging procedures. (5) The small amounts of dye that remain associated with the marrow graft and are infused into the patient are approximately 100 000‐fold less than the LD10 (in mice) and therefore unlikely to cause any harm. The outcome of the first clinical application of the technique supports this view (Sieber et al., 1986c).A better understanding of the underlying molecular mechanisms will undoubtedly lead to more effective applications of the technique and perhaps to the identification of more potent analogs of MC 540.
CLINICAL LASER PHOTODYNAMIC THERAPY IN THE TREATMENT OF BLADDER CARCINOMA
Authors: Shumaker B. P. , Hetzel F. W. 
Published: January 2008

Abstract The treatment of bladder carcinoma using dihematoporphyrin ether (DHE) and laser photodynamic therapy (PDT) is described herein. Patients selected for this study have cytology‐ and biopsy‐proven transitional cell carcinoma, no histologic evidence of muscle invasion, and negative excretory urograms.Sixteen patients have been treated, with follow‐up from 6 to 36 months. Eleven have had a complete response, and 3 a partial response in that they required re‐treatment for recurrence. Two of these patients have not recurred at this time. One of the patients who recurred had tumor extension into the prostatic urethra and has been successfully re‐treated (disease‐free at 6 months). There was one treatment failure and 1 patient lost to follow‐up.Photosensitivity for up to 4 weeks is a known side‐effect, but unexpected morbidity included a transient but significant increase in urinary frequency, urgency, and occasionally hematuria which spontaneously resolved within 3‐4 weeks. Careful placement of the fiberoptic tip in the centre of the bladder, bladder distension during treatment with saline rather than water, the instillation of the minimum volume required to “smooth out” the mucosa for complete bladder photoradiation, and delivered energy of 25 J cm’or less may have prevented the more severe complications (i.e. bladder shrinkage) reported by Dougherty and Nseyo (personal communication).We also feel that there is some early evidence that a heightened immune response (similar to intravesical BCG) may potentially play some role in explaining the efficacy of PDT in long disease‐free intervals, although this is just a histologic observation at present.It appears the PDT offers another practical treatment modality for non‐invasive transitional cell carcinoma in patients refractory to standard surgical and chemotherapeutic regimens, and has been addressed by numerous other investigators such as Benson (1985) and Hisazumi (1983). We are presently recommending to our patients in these categories to undergo a course of PDT prior to relinquishing to cystectomy.
FLAGELLUM AUTOFLUORESCENCE and PHOTOACCUMULATION IN HETEROKONT ALGAE
Authors: Müller D. G. , Maier I. , Müller H. 
Published: January 2008

AbstractZoids of various brown algae capable of positive or negative phototaxis show strong autofluorescence of their posterior fiagellum and flagellar swelling when excited with blue light of 450 nm. This effect is lacking in zoids without stigma and phototactic capability. Fluorescence studies on living cells point to a flavin as photoreceptor pigment. The spectral sensitivity curve of photoaccumul‐ation suggests a carotenoid pigment (maximum 430–450 nm) being involved, with no effect below 380 nm and above 540 nm. The results obtained in this study indicate a flavin as photoreceptor pigment, which is periodically shaded by a carotenoid stigma.
INTERMEDIATES IN THE PHOTOCONVERSION OF FUNCTIONAL PHYTOCHROME IN FERN SPORES OF Dryopteris–II. In vivo KINETICS OF THE DECAY OF Ii700 AND OF THE FORMATION OF Pfr STUDIED WITH A DOUBLE‐LASER APPARATUS*
Authors: Scheuerlein R. , Inoue Y. , Furuya M. 
Published: January 2008

Abstract— Photoconversion of the red‐light‐absorbing form of phytochrome, Pr, to the far‐red‐light‐absorbing form, Pfr, was investigated in vivo at 22°C with 600 or 800 ns laser pulses of high spectral purity and induction of spore germination in Dryopteris paleacea was used as indicator for the progress of photoconversion. This reaction is initiated by a saturating R‐laser pulse of 648.5 nm, establishing an equilibrium of the photochromic system between Pr and the very early intermediates, Ii700 (Prφ Ii700)‐ The decay of Ii700 as well as the formation of Pfr was recorded by the application of a second pulse varied between 698 and 717.5 nm, which inhibits the formation of Plr being absorbed predominantly by Ii700or Pfr, respectively.The most effective inhibition for the second pulse is found up to 10 u.s after the first pulse and this is interpreted by photoreversion of Ii700 to Pr; thus reducing the formation of Pfr from Ii700. This early inhibition decreases between 10 μs to 100 ms after the R‐laser pulse, as a result of the decay of Iibl to a bleached species I,;. This decay can be described by three first order kinetics with the rate constants k12= 16830 ± 2970 s‐1, k12= 666 ± 218 s‐1,k13= 9.8 ± 0.9 s‐1. A second inhibition, due to the formation of Pfr, is found for dark intervals <100 ms and can be described by two first order kinetics with the rate constants k21= 2.9 ± 0.6 s‐1 and k22= 0.17 s‐l.
OXYGEN CONSUMPTION AND LUMINESCENCE OF ISOLATED Porichthys PHOTOPHORES IN RESPONSE TO ADRENERGIC STIMULATIONS
Authors: Mallefet J. , Baguet F. 
Published: January 2008

Abstract—Isolated photophores of Porichthys maintained in saline at 20oC, consume oxygen at a mean rate of 115 ± 5 ± 10 3 nmol O2 min1 (n= 165).In the presence of 0.1 and 1 mM adrenalin or noradrenaline the photophore produces a fast peak of light followed by a slow luminescence. A large increase in oxygen consumption occurs prior to the fast light response and it remains slightly above the resting level during the following slow light emission.When isolated photophores do not produce the fast peak of light(in response to isoprenalin or after treatment with phentolamine), there is only a slight transient increase of oxygen consumption. During the production of the slow luminescence the oxygen consumption remains close to the resting level.A relationship between the oxygen consumption and the light emission during the fast luminescence has been found: it is suggested that most of the oxygen consumed could be involved in a triggering mechanism of light production.
MOLECULAR MECHANISM OF DRUG PHOTOSENSITIZATION–II. PHOTOHEMOLYSIS SENSITIZED BY KETOPROFEN
Authors: Costanzo L.L. , Guidi G.De , Condorelli G. , Cambria A. , Fama M. 
Published: January 2008

Abstract—Red blood cell lysis photosensitized by ketoprofen (KPF) was investigated. The photohem‐olysis was inhibited by butylated hydroxyanisole, reduced glutathione, superoxide dismutase and mannitol, and was unaffected by sodium azide; the presence of oxygen markedly enhanced the lysis. Photohemolysis was also observed under anaerobic conditions. Ketoprofen, irradiated in aqueous buffer solution at pH 7.4, underwent a decarboxylation process via intermediate radicals, leading to the compounds (3‐benzoylphenyl)ethane, (3‐benzoylphenyl)ethyl hydroperoxide, (3‐benzoylphenyl)‐ethanol and (3‐benzoylphenyl)ethanone under aerobic conditions and only to the compound (3‐benzpylphenyl)ethane under anaerobic conditions.The four photoproducts showed lytic activity, particularly high for the alcohol and hydroperoxide.The overall results suggest for KPF‐photosensitized hemolysis a molecular mechanism involving free radicals, superoxide anion and sensitizer photodegradation products.
DNA LESIONS AND DNA DEGRADATION IN MOUSE LYMPHOMA L5178Y CELLS AFTER PHOTODYNAMIC TREATMENT SENSITIZED BY CHLOROALUMINUM PHTHALOCYANINE
Authors: Ramakrishnan Narayani , Oleinick Nancy L. , Clay Marian E. , Horng Min‐Fen , Antunez Antonio R. , Evans Helen H. 
Published: January 2008

Abstract—Two closely related strains of mouse lymphoma L5178Y cells, LY‐R and LY‐S, have been found to differ in their sensitivity to the cytotoxic effects of photodynamic treatment (PDT) with chloroaluminum phthalocyanine (CAPC) and red light. Strain LY‐R is more sensitive to photodynamic cell killing than strain LY‐S. Differences in uptake of CAPC could not account for the differences in cytotoxic effects. There was no marked difference between the two strains in the induction of single‐strand breaks (which includes frank single‐strand breaks and alkali‐labile lesions), but substantially more DNA‐protein cross‐links were formed in strain LY‐R by CAPC and light. Repair of single‐strand breaks proceeded with similar kinetics in both strains for the first 30 min post‐irradiation, suggesting that these lesions are not responsible for the differential sensitivity of the two strains to the lethal effects of photodynamic treatment. Thereafter, alkaline elution revealed the presence of increasing DNA strand breakage in strain LY‐R. DNA degradation, as measured by the conversion of prelabled [14C] DNA to acid‐soluble radioactivity, was more rapid and extensive in strain LY‐R.
In vitro PHOTOSENSITIZATION WITH A BENZOPORPHYRIN DERIVATIVE
Authors: KESSEL DAVID 
Published: January 2008

AbstractBiophysical and photobiological properties of two benzoporphyrin derivatives were examined. These dyes exhibit substantial absorbance in the red, and are potent photosensitizers in vitro. After brief (0.5 h) incubations, phototoxicity was more closely correlated with membrane than with mitochondrial photodamage. Affinity of these dyes toward plasma lipoproteins are consistent with a mode of localization via the LDL‐mediated mechanism utilized by the hematoporphyrin‐derived product, HPD.
PHYTOCHROME ACTION AT HIGH PHOTON FLUENCE RATES: RAPID EXTENSION RATE RESPONSES OF LIGHT‐GROWN MUSTARD TO VARIATIONS INFLUENCE RATE and RED: FAR‐RED RATIO*
Authors: Smith Harry 
Published: January 2008

Abstract— Extension growth rate of light‐grown mustard (Sinapis alba L.) seedlings was monitored continuously using a sensitive linear displacement transducer system. When high fluence rates (ca 2 mmol m−2 s_1) of mixed red and far‐red light were presented to the growing internodes from fibre optic probes, fluctuations in extension rate occurred during the first 30 min. High red: far‐red ratios (R: FR) caused growth deceleration, whilst low R: FR caused transitory growth acceleration. These changes in extension rate were not exactly as predicted from the proportions of Pr (the red‐absorbing form of phytochrome) and Pfr (the far‐red absorbing form of phytochrome) calculated to be established by the light sources. Nevertheless, the data demonstrate that phytochrome is able to control extension growth at fiuence rates approaching those of summer sunlight, thereby providing the capacity to sense the presence of neighbouring vegetation before shading seriously compromises photosynthesis.Varying fiuence rate over two orders of magnitude whilst maintaining R: FR constant evoked transient fluctuations in extension rate. At high R: FR, a 100‐fold step down in fiuence rate led, after a lag of ca 10 min, to a transient (i.e. 20 min) deceleration of extension that was followed by a marked transient (i.e. 20 min) acceleration. After a 100‐fold step up in fiuence rate, a transient (i.e. 20 min) acceleration only was observed, beginning after a lag of ca 10 min. When R: FR was low, neither a step‐down nor a step‐up in fluence rate resulted in appreciable fluctuations in extension rate.The data are discussed in relation to the possible role played by the accumulation of photoconversion intermediates using a simple computer model for simulating active phytochrome concentrations at high fluence rates. The possibility that the mechanism for the photoperception of light quality by phytochrome may be capable of rapid adaptation to fluence rate fluctuations is proposed.
PHOTOINDUCED ELECTRON TRANSFER
Authors: Fox Marye Anne 
Published: January 2008

Abstract— Given the pre‐eminent roles of photoinduced electron transfer and energy transfer as primary events in photobiology, it is incumbent on practitioners of the science to understand those principles which govern these elementary events. Recent developments in both theory and experiment on photoinduced electron transfer have allowed for important insights into understanding the factors governing such steps. For example, shown in Fig. 1 is a representation of the positions of the chromophores in the photosynthetic reaction center of Rhodopseudomonas sphaeroides, as determined from crystallographic measurements (Chang et al., 1986), showing that its three dimensional arrangement within an intact membrane is analogous to that observed earlier in Rhodopseudomonas viridis (Deisenhofer et al., 1984). In both systems, the critical event of photosynthesis is the transfer of an electron from the photoexcited special pair of bacteriochlorophylls located at the top via the pheophytin at the far right to the quinone at the bottom which acts as an ultimate repository for the separated charge. Of great importance is a determination of those factors which govern the efficiency and the rate of electron transfer through this photoinduced cascade and a better understanding of how this fixed, prearranged structure maximizes the efficiency of photochemical energy storage.Although the reaction center represents nature's most graphic and most detailed connection between the experimental and theoretical models of photoinduced electron transfer, much of the physical insight into this process has been developed on simpler organic molecules. Rattier than focusing on the details of photosynthesis, this article will concentrate on recent developments in model systems which evaluate the relative importance of factors influencing the efficiency and rates of excited state induced electron transfer. We introduce these concepts at a level appropriate for the scientifically literate biologist who has not heretofore been concerned with such details. Since this is an overview article, few citations of the original literature will appear, and the interested reader should refer to any number of excellent topical reviews which consider specific aspects of photoinduced electron transfer for further investigation (Fox and Chanon, 1989; Pac and Oshitani, 1989).
QUINONE SENSITIZED ELECTRON TRANSFER PHOTOOXIDATION OF NUCLEIC ACIDS: CHEMISTRY OF THYMINE AND THYMIDINE RADICAL CATIONS IN AQUEOUS SOLUTION*
Authors: Wagner J. R. , Lier J‐ E. van , JOHNSTON L. J. 
Published: January 2008

Abstract—The 2‐methyl‐l,4‐naphthoquinone (MQ) sensitized photooxidation of nucleic acid derivatives has been studied by laser flash photolysis and steady state methods. Thymine and thymidine, as well as other DNA model compounds, quench triplet MQ by electron transfer to give MQ radical anions and pyrimidine or purine radical cations. Although the pyrimidine radical cations cannot be directly observed by flash photolysis, the addition of N,N,N',N'‐tetramethyl‐l,4‐phenylenediamine (TMPD) results in the formation of the TMPD radical cation via scavenging of the pyrimidine radical cation. The photooxidation products for thymine and thymidine are shown to result from subsequent chemical reactions of the radical cations in oxygenated aqueous solution. The quantum yield for substrate loss at limiting substrate concentrations is 0.38 for thymine and 0.66 for thymidine. The chemistry of the radical cations involves hydration by water leading to C(6)‐OH adduct radicals of the pyrimidine and deprotonation from the N(l) position in thymine and the C(5) methyl group for thymidine. Superoxide ions produced via quenching of the quinone radical anion with oxygen appear to be involved in the formation of thymine and thymidine hydroperoxides and in the reaction with N(l)‐thyminyl radicals to regenerate thymine. The effects of pH were examined in the range pH 5–8 in both the presence and absence of superoxide dismutase. Initial C(6)‐OH thymine adducts are suggested to dehydrate to give N(l)‐thyminyl radicals.
IS SINGLET OXYGEN FORMATION DOMINANT IN TRIPLET QUENCHING PROCESSES? MEASUREMENT OF THE QUANTUM YIELD OF SINGLET OXYGEN FORMATION BY THE TIME‐RESOLVED THERMAL LENS METHOD
Authors: Terazima Masahide , Tonooka Mizuho , Azumi Tohru 
Published: January 2008

AbstractThe quantum yields of singlet oxygen formation (ØΔ) by the quenching of triplet states of organic sensitizers are measured at various concentrations of the sensitizers by using the time‐resolved thermal lens method. Above a certain concentration, ØΔ is independent of the sensitizer concentration. Below the threshold, ØΔ gradually decreases as the concentration of the sensitizer decreases. The extrapolation of ØΔ to zero concentration indicates that singlet oxygen formation is not necessarily dominant in the quenching process even for the 3ππ* state in benzene.
SPECTROSCOPIC OBSERVATION OF SOLVENT INTERACTION WITH SELECTED RETINAL SCHIFF BASES*
Authors: Blatz Paul E. , Mohler JonathanH. , Ahmed Wasi 
Published: January 2008

AbstractIodide salts of several N‐retinylidenedialkylamines were prepared and their UV‐VIS spectra recorded. Their γmax values increased as the number of hydrogen atoms on the carbons alpha to nitrogen increased. In separate experiments, iodide salts of N‐retinylidene‐n‐butylammonium (1) and N‐retinylidene‐n‐butylmethylammonium (2) were prepared, and their excitation energies (ΔE) were measured in selected solvents of varying dielectric constant Data from each compound gave a straight line which converged at ε= 0. On the other hand, when ΔE values of the iodide and bromide of 2 were plotted vs solvent e, parallel rather than convergent lines were obtained. When γmax values of 1 and 2 were measured in a greater number of solvents, the solvents fell into four main groups. The first group, regular solvents, are rigid, have fixed dipoles, neither donate nor accept H‐bonds, and the δE of 1 and 2 decreases linearly as solvent e increases. This line for 2 is taken as a standard against which other solvents are judged. A second class of solvents that are good H‐bond donors like CHCl3, whose dipole moment coincides with the CH bond axis, is located in an area below the standard line. A third group, nucleophilic solvents like tetrahydrofuran, whose dipole moment is coincident with a strongly nucleophilic oxygen atom are good H‐bond acceptors and are found above the standard line. Solvents with unpredictable spectroscopic behavior are classed as anomalous.