bluuebunny/crossref_metadata_2025 huggingface dataset:
TIME‐RESOLVED RESONANCE RAMAN STUDIES ON THE PHOTOCHEMICAL CYCLE OF BACTERIORHODOPSIN
Authors: Alshutn T. , Stockburger M.
Published: January 2008

Abstract— Kinetic resonance Raman (RR) experiments were designed to study the time‐behaviour of the retinal‐binding protein bacteriorhodopsin (BR) in its photochemical cycle. The unphotolyzed chro‐mophore B‐570 and the two intermediates L‐550 and M‐412 were probed by the characteristic C=C stretching vibrations of the retinal moiety. Time resolution was achieved with a spinning cell as flow system in combination with two CW lasers in a pump‐probe configuration. RR spectra were probed at 475 nm at various delay times between pump and probe event. The deconvolution of the spectra into the various components B‐570, L‐550 and M‐412 was carried out by curve fitting procedures. It was found that at pH7.4 L‐550 decays — with a time‐constant of 62 μs — not completely but to a residual level of 35% of its initial value. This intermediate L‐amplitude finally disappears in the ms‐range (4.5 ms) synchroneously with the intermediate M‐412. An analogeous time‐behaviour was found at pH 4.6. In the basic range also an “L” ‐intermediate could be identified which is coupled to the long‐lived M‐component. To explain the peculiar time‐dependence it is proposed that during the fast decay of L a dynamic equilibrium between L and M is established. Then during the reconstitution of B‐570 the two intermediates disappear synchroneously. A molecular model is presented in which the dynamic equilibrium between L and M is explained by an oscillatory motion of a proton from the Schiff base group of the chromophore to its counterion.
AN ACTION SPECTRUM FOR BLUE AND NEAR ULTRAVIOLET IN ACTIVATION OF Propionibacterium acnes; WITH EMPHASIS ON A POSSIBLE PORPHYRIN PHOTOSENSITIZATION
Authors: Kjeldstad Berit , Johnsson Anders
Published: January 2008

—Propionibacterium acnes (P. acnes), grown on Eagles medium with different pH. were irradiated with monochromatic light in the range 320 to 440 nm. Different pH leads to different porphyrin concentrations in the cells. The light sensitivity of the bacteria was estimated from the reduction in their ability to form colonies after radiation. The sensitivity was highest for the lowest wavelength (320 nm). and decreased continuously with increasing wavelength up to 380 nm. In the region between 380 and 440 nm there was a second maximum (at 415 nm) which corresponds to the maximum absorption ol the fluorescing porphyrins in P. acnes. The sensitivity to 415 nm light was found to be dependent on the endogenous porphyrin concentration in the cells. while the sensitivity to 320 nm radiation was independent of the amount of porphyrin present. These results indicate that porphyrins produced by the bacteria are important for the light sensitivity of these bacteria.
IN SITU HYDROGEN PEROXIDE PRODUCTION MAY ACCOUNT FOR A PORTION OF NUV (300–400 nm) INACTIVATION OF STATIONARY PHASE Escherichia coli
Authors: Hartman Philip S.
Published: January 2008

Abstract— Pre‐irradiation of stationary phase cells of Escherichia coli K‐12 with broadband near‐UV radiation potentiates the lethal effects of subsequent exposure to near‐UV radiation plus hydrogen peroxide. Identical fluences failed to modulate killing due to far‐UV radiation. These data indicate that biologically revelant levels of hydrogen peroxide may be generated in situ upon the near‐UV irradiation of cells.
DECAY KINETICS OF THE TRIPLET EXCITED STATE OF LUMIFLAVIN
Authors: Naman S. A. , Tegnér L.
Published: January 2008

Abstract— The rate of decay of the triplet state of lumiflavin in deaerated phosphate buffer at pH 6.9, has been studied using the flash photolysis technique, at various concentrations and flash energies. The decay of the transient appears as a mixture of first and second order processes, the relative importance of which depends on the experimental conditions.

The following competitive reactions have been found to explain the course of the reaction of the triplet excited state of lumiflavin.
EVIDENCE FROM PHOTOREACTIVATION KINETICS FOR MULTIPLE DNA PHOTOLYASES IN YEAST
Authors: Johnson Ronald G. , Haynes Robert H.
Published: January 2008

Abstract— We have analyzed the kinetics of photoreactivation of ultraviolet‐light‐irradiated cells of two strains of the yeast Saccharomyces cerevisiae. The analysis yields plots of h(t), the number of photorepairable lethal hits remaining in the cell as a function of the time t of exposure to a continuous source of photoreactivating light. In the case of one of the strains studied, an excision‐deficient haploid strain, it is found that the time‐dependence of h(t) is given by the sum of three decreasing exponential functions of t for stationary phase cultures grown at 23 or 30°C. When the culture is grown at 37°C. the fastest component is absent and the intermediate component is reduced in importance relative to the remaining slow component. In the case of the other strain, a diploid of wild‐type radiation resistance, h(t) is found to contain just one decreasing exponential for cultures grown at 23, 30, and 37°C. The rate constant depends on the growth temperature of the cells, decreasing with increasing temperature. The results are interpreted as evidence for multiple DNA photolyases in the sensitive haploid strain.
Na+/K+ TRANSPORT AND PHOTOSENSITIVITY OF THE COLORLESS FLAGELLATE Peranema trichophorum (Euglenida)
Authors: Mikolajczyk Ewa
Published: January 2008

Abstract— Perimycin, ouabain and elevation of extracellular K+ concentrations cause an increase in the fluence rate thresholds (white light) for the step‐up photophobic response in Peranema trichophorum. Elevation of extracellular Na+ concentration decreases the thresholds for this response in comparison to the control level. The fluence rate threshold of perimycin‐treated cells increases before the side effect of an antibiotic action appears. Removal of K+ ions from the medium of K+‐treated cells to a concentration of 1 mM depresses the threshold for the step‐up response to the control level. By addition of K+ or Na + ions to perimycin‐ or ouabain‐treated cells the threshold returns to the control value. It is suggested that the flagellar and cell membrane are responsible for changes of P. trichophorum photosensitivity.
A NEW DIAZIRINE FOR PROTEIN MODIFICATION BY FLASH PHOTOLYSIS: COMPARISON WITH AN AZIDE
Authors: Johnson David F. , Brown Ray K.
Published: January 2008

Abstract— A new photolabeling agent, N‐[4–(3‐chlorodiazirin‐3‐yl)benzoyl]glycine (CDBG), a carbene generator, was synthesized. The incorporation of its photolytic products into egg white lysozyme was studied using flash photolysis and compared with incorporation of N‐(4‐azido‐2‐nitro‐phenyl)‐2‐amino ethane sulfonate (NAPT) products into lysozyme and bovine pancreatic ribonuclease A. There was considerable additional incorporation of photolysis products into ribonuclease and lysozyme after termination of flash photolysis when NAPT was used but no additional incorporation when CDBG was used. Protein labeled with NAPT retained the label poorly during electrophoresis in sodium dodecyl sulfate. Lysozyme labeled with CDBG lost little label upon electrophoresis. Neither label was well retained during electrophoresis in 8 M urea. Peptic and tryptic peptides from CDBG labeled lysozyme were differentially labeled.
PETITE INDUCTION IN YEAST, Saccharomyces cerevisiae, BY PHOTOACTIVATION OF 3‐A‐ZIDO‐6‐A‐MINO‐10‐M‐ETHYLACRIDINIUM CHLORIDE
Authors: Iwamoto Y. , Yanagihara Y. , Yielding L. W.
Published: January 2008

Abstract— The photoinduction of petite colonies and cell toxicity in non‐growing yeast, Saccharomyces cerevisiae, by 3‐a‐zido‐6‐a‐mino‐10‐m‐ethylacridinium chloride (AAMAC) has been examined. The results presented here indicate that mitochondrial DNA damage in resting yeast which occurs following irradiation of AAMAC‐treated cells for short time periods is probably mediated through a covalent adduct between AAMAC and DNA. Furthermore, the photoreaction which contributes to biological activity is dependent on the presence of oxygen. Pre‐irradiated AAMAC, which no longer exhibited the short‐term photo‐induction of biological effects showed a second biological activity. In this case longer irradiation times, e.g. 30 min, were required to induce petites for resting yeast. Again there was a strong dependence on the presence of oxygen. These results suggest that both processes may be effected through oxygen intermediates (photodynamic processes).
REDUCED REPAIR OF NON‐DIMER PHOTOPRODUCTS IN A GENE TRANSFECTED INTO XERODERMA PIGMENTOSUM CELLS
Authors: Protić‐Sabljić Miroslava , KRaemer Kenneth H.
Published: January 2008

Abstract— 4ells from patients with the sun sensitive cancer‐prone disease, xeroderma pigmentosum (XP) have defective repair of UV damaged DNA with reduced excision of the major photoproduct, the cyclobutane type pyrimidine dimer. Other (non‐dimer) photoproducts, have recently been implicated in UV mutagenesis. Utilizing an expression vector host cell reactivation assay, we studied UV damaged transfecting DNA that was treated by in vitro photoreactivation to reverse pyrimidine dimers while not altering other photoproducts. We found that the reduced expression of a UV damaged transfecting plasmid in XP complementation group A cells is only partially reversed by photoreactivation. E. coli photolyase treatment of pSV2catSVgpt exposed to 100 or 200 J m−2 of 254 nm radiation removed 99% of the T4 endonuclease V sensitive sites. Transfection of XP12BE(SV40) cells with photoreactivated pSV2catSVgpt showed residual inhibition corresponding to 25 to 37% of the lethal hits to the cat gene. This residual inhibition corresponds to the fraction of non‐dimer photoproducts induced by UV. This result implies that XP12BE(SV40) cells do not repair most of the non‐dimer photoproducts in DNA.
SENSITIZER‐INDUCED CONFORMATIONAL CHANGES IN LENS CRYSTALLIN—I. PHOTODYNAMIC ACTION OF METHYLENE BLUE AND N‐FORMYLKYNURENINE ON BOVINE α‐CRYSTALLIN
Authors: Mandal Krishnagopal , Bose Swapan K. , Chakrabarti Bireswar
Published: January 2008

Abstract— Fluorescence and circular dichroic properties of bovine a‐crystallin have been monitored to detect changes in the structural integrity of the protein following photoreactions in the presence of sensitizer, either methylene blue or N‐formylkynurenine. Methylene blue‐sensitized photooxidation causes a change in the tertiary structure as manifested in the near‐UV CD; this is observed within 0.5 h of irradiation during which time tryptophan emission decreases rapidly. Using inhibitors specific for active species of oxygen, it has been shown that singlet oxygen predominantly causes this change but the sensitizer molecules also have some role in this process. Upon 6 h of irradiation in the presence of methylene blue under both aerobic and anaerobic conditions, the thiol groups that were in a non‐polar region of the protein are exposed to polar environments. In conformity with these fluorescence results. near‐UV CD (tertiary structure) suffers a drastic alteration whereas the far‐UV CD (secondary structure) remains virtually unchanged. The studies with inhibitors indicate that sensitizer molecule itself is primarily responsible for this process. This major change in the conformation has been explained by suggesting that a large portion of the protein unfolds in the photosensitized reaction, thereby altering microenviron‐ments, orientation, and intermolecular interactions of different amino acids. N‐formylkynurenine also shows some changes in the near‐UV CD, presumably, caused by H2O2 generated in the photosensitized reaction. But the major alteration in the microenvironments of thiol groups and in the near‐UV CD, as observed in the case of methylene blue, does not occur even when the protein is irradiated for 6 h in the presence of N‐formylkynurenine and air.
PHOTOSYSTEM II HETEROGENEITY IN THE MARINE DIATOM Phaeodactylum tricornutum
Authors: Owens Thomas G.
Published: January 2008

Abstract— The kinetics of photosystem II photochemistry are analyzed in the marine diatom Phaeodacfylum tricornutum by measurement of fluorescence induction in cell suspensions treated with 3–(3,4‐dichlorophenyl)‐1,1‐dimethylurea. Photosystem II kinetics are found to be biphasic, the sum of two exponential components, suggesting that biphasic energy conversion in photosystem II may be a general consequence of thylakoid membrane appression. The emission wavelength‐dependence of fluorescence induction suggests that the two photosystem II components have different variable fluorescence emission spectra. The slower component exhibits characteristic emission of the diatom light‐harvesting complexes while emission from the faster component resembles that of the photosystem II reaction center. Variable fluorescence emission (293 K) at wavelengths > 700 nm is assigned to photosystem II. Application of model equations indicates that the two photosystem II unit types differ primarily in antenna size. A new analytical procedure is presented which eliminates ambiguities in the kinetic analysis associated with the incorrect assignment of the maximal fluorescence yield.
MECHANISM OF ORIENTATION AND LINEAR DICHROISM OF PHOTOSYNTHETIC PARTICLES IN ELECTRIC FIELDS: CHLOROPLASTS AND CHLOROPHYLL‐PROTEIN COMPLEXES
Authors: Gagliano A. G. , Geacintov N. E. , Breton J.
Published: January 2008

Abstract— The mechanisms of orientation in pulsed and alternating electric fields of thylakoids (derived from the sonication of spinach chloroplasts) and of light‐harvesting chlorophyll a/b‐protein complexes (CPII) were investigated by utilizing linear dichroism techniques. Comparisons of the linear dichroism spectra of thylakoids and CPII particles suggest that the latter are oriented with their directions of largest electronic polarizabilities (and thus probably their largest dimensions) within the thylakoid membrane planes. At low electric field strengths (< 12 V cm−1), and at low frequencies of alternating electric fields (< 0.25 Hz), thylakoid membranes tend to align with their normals parallel to the direction of the applied electric field; the mechanism of orientation involves a permanent dipole moment of the thylakoids which is oriented perpendicular to the planes of the membranes. However, at high field strengths and high frequencies of the applied alternating electric fields, the thylakoids tend to orient with their planes parallel to the applied field, thus exhibiting an inversion of the sign of the linear dichroism as the electric field strength is increased. At the higher frequencies and at higher field strengths, the orientation mechanisms of the thylakoids involve induced dipole moments related to anisotropies in the electronic polarizabilities. The polarizability is higher within the plane than along a normal to the plane, thus accounting for the inversion of the dichroism as the electric field strength is increased. The CPII particles align with their largest dimension parallel to the applied field at all field strength, indicating that the induced dipole moment dominates the orientation mechanisms in pulsed electric fields. The magnitude of the absolute linear dichroism of CPII suspensions increases with increasing dilution, indicating that aggregates of lower symmetry are formed at higher concentrations of the CPII complexes.
EFFECT OF GROWTH TEMPERATURE ON LIPID COMPOSITION and ULTRAVIOLET SENSITIVITY OF HUMAN CELLS
Authors: McAleer M. A. , Moore S. P. , Moss S. H.
Published: January 2008

Abstract Human skin fibroblasts were incubated at either 25 or 37°C before UV irradiation. Cells incubated at 25°C were more resistant to near UV radiation than cells grown at 37°C, but cells grown at the lower temperature were more sensitive to 254 nm radiation. Fatty acid analysis of membranes of cells showed that cells incubated at the lower temperature contained significantly higher amounts of linoleic acid (18:2) and linolenic acid (18:3) than cells incubated at 37°C. To determine if this difference in fatty acid content of the membranes was responsible for the UV survival characteristics of cells incubated at different temperatures, cells were enriched with either linoleate or linolenate during a 37°C incubation period. Gas chromatography revealed that cells incorporated the supplied fatty acid. Fatty acid enriched cells were then irradiated with near UV, and survival characteristics were compared to those obtained with cells grown at the lower incubation temperature. The results suggest that the different proportion of fatty acid content of the cells is not the cause of different UV sensitivities of cells grown at 25°C compared to cells grown at 37°C.
CHARACTERIZATION OF INTRA‐TUMORAL PORPHYRIN FOLLOWING INJECTION OF HEMATOPORPHYRIN DERIVATIVE OR ITS PURIFIED COMPONENT*
Authors: Dougherty Thomas J. , Mang Thomas S.
Published: January 2008

Abstract Photodynamic therapy (PDT) utilizes either hematoporphyrin derivative (Hpd) or a purified form of Hpd termed DHE, as photosensitizers for treatment of a variety of solid tumors in man. The reasons for long retention of these porphyrins in a wide range of histologically diverse tumors remain obscure. We have found that the RIF fibrosarcoma and SMT‐F mammary carcinoma in mice, a intrapancreatic tumor in the hamster and a tumor removed from a patient with a myxoid sarcoma, may take up Hpd or DHE by endocytosis. On the other hand, the RIF tumor cells in vitro show a tendency for selective uptake and retention of the more hydrophobic components of the mixture.
LOSS OF PHOTOREVERSIBILITY OF SUNBURN CELL INDUCTION IN Monodelphis domestica
Authors: Ley Ronald D. , Applegate Lee A.
Published: January 2008

Exposure of the South American opossum, Monodelphis domestica, to ultraviolet radiation (UVR) resulted in the formation of sunburn cells (SBCs) in the epidermis. If, however, the UVR was immediately followed by an exposure to photoreactivating light, which reversed ∼ 95% of the UVR‐induced pyrrolidine dimers in epidermal DNA, the appearance of SBCs was suppressed by ∼ 90%. Delaying the photoreactivation (PR) treatment resulted in a progressive loss with time in the capacity of the PR treatment to suppress SBC induction. PR treatment administered 12 h after UVR exposure resulted in only an ∼ 11% suppression of SBC formation even though ∼ 97% of the remaining pyrimidine dimers were repaired by the PR exposure.
MICELLAR EFFECT ON THE FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS BY AMINOACIDS
Authors: Bertolotti S. G. , Bohorquez M. DEL V. , Cosa J. J. , Garciaand N. A. , Previtali C. M.
Published: January 2008

The effect of anionic and cationic micelles on the fluorescence quenching of indolic compounds by aliphatic aminoacids has been studied. Sodium dodecyl sulfate (SDS) micelles increase the quenching efficiency of glycine, alanine, valine and leucines up to a factor of two. On the other hand, cetyltrimethyl ammonium (CTAB and CTAC) micelles reduce the quenching. For sulfur containing aminoacids (methionine and cysteine) both SDS and CTAC reduce the quenching. The inhibitory effect is larger for CTAC. Linear Stern‐Volmer plots were obtained and in the case of SDS lifetime measurements indicate that the quenching is of dynamic nature.

The results were interpreted by a model which assumes that aminoacids can interact with SDS micelles. Partition constants of the order of unity were estimated. For CTAC the aminoacids are not able to interact with the micelles.
INCREASED ENERGY TRANSFER FROM PHYCOBILISOMES TO PHOTOSYSTEM II IN HIGH LIGHT ADAPTED Anabaena cylindrica
Authors: Laczkó Ilona , Kaiseva Elizabeth
Published: January 2008

Excitation energy transfer from phycobilisomes to photosystem II in high‐light adapted cells of Anabaena cylindrica was studied by fluorescence spectroscopy and compared to that of low‐light adapted cells. Measurements were made on membrane fragments containing phycobilisomes, photosystem I and II, isolated in 0.75 M K‐phosphate. Relative efficiency of 430 to 590 nm light in the excitation of F680 chlorophyll fluorescence was compared in low and high light adapted cells, respectively. The values indicate that light energy absorbed by phycobilisomes is transferred to photosystem II antenna chlorophylls with higher efficiency in high‐light adapted cells than in low‐light adapted cells. Partial dissociation and uncoupling of energy transfer caused by low ion concentration were different in the membrane fragments isolated from the two kinds of cells and indicated a higher aggregation state of pigment‐protein complexes of phycobilisomes in high‐light adapted A. cylindrica cells.
CAROTENOIDS AFFECT DEVELOPMENT OF UV‐B INDUCED SKIN CANCER
Authors: Mathews‐Roth Micheline M. , Krinsky Norman I.
Published: January 2008

One large dose of UV‐B (8 × 1014 J m‐2: 290‐320 nm) has been found to cause the development of skin tumors in hairless mice, and carotenoid pigments prevent or delay tumor development in this system. This model was used to determine if the protective effect of carotenoid pigments against UV‐B induced skin tumors occurred during the induction phase or progression phase of UV‐B carcinogenesis. The results indicate that the carotenoids canthaxanthin and (J‐carotene interfered with the progression phase in this system; whether they also had an effect during induction could not be definitely determined from our data.
INDUCTION OF CHLOROPLAST MOVEMENT IN THE ALGA Mougeotia BY POLARIZED NANOSECOND DYE‐LASER PULSES*†
Authors: Scheuerlein R. , Braslavsky S. E.
Published: January 2008

Chloroplast movement of white‐light treated alga Mougeotia was induced by 15‐ns dye‐laser pulses (620‐690 nm). A single pulse, polarized perpendicular to the cell axis, does not induce a significant response, although full response can be obtained when the same fluence is applied during a 30‐s irradiation. However, for 620 and 660 nm perpendicularly polarized flash irradiation results in a significant response, if the total fluence is given by 2 consecutive flashes with 2‐s dark interval (double‐flash effect), and full response can be obtained by poly‐flash induction. Flashes of 690 nm in no case induce a response. Similar to the case of lettuce‐seed germination (Scheuerlein and Braslavsky, 1985), the establishment of a photochromic system between Pr and the very early intermediates (= lumi‐R) during the 15‐ns laser pulse can explain the results. At 690 nm, the photochromic system is shifted more extensively to Pr than at shorter wavelengths; thus, Pfr formation is strongly diminished. At shorter wavelengths (620 and 660 nm) the inhibition of Pfr formation by the existence of this photochromic system is smaller. The results are compatible with parallel dipole moments of the chromophores in Pr and in the first intermediates.

A smaller but still significant response is obtained for repeated pulses of 660‐nm light, polarized parallel to the cell axis. These results are explained by a gradient in light sensitivity around the cell axis (induced by the white‐light pretreatment) and an increasing Plr concentration, established around the cell axis, as a function of the number of pulses.
SPINACH PLASTOCYANIN AS AN ELECTRON ACCEPTOR FROM MEMBRANE‐BOUND CHLOROPHYLL TRIPLET STATE IN POSITIVELY CHARGED LIPID BILAYER VESICLES*
Authors: Senthilathipan Velu , Tollin Gordon
Published: January 2008

Spinach plastocyanin is bound to egg phosphatidylcholine vesicles containing 5–25 mole percent dioctadecyldimethylammonium chloride (DODAC) via electrostatic interactions in a 50 mM betaine medium (pH=6.5). This was demonstrated by both gel filtration experiments and kinetic results using laser flash photolysis. Under those conditions, oxidized plastocyanin can function as a direct electron acceptor from membrane‐bound triplet chlorophyll to produce chlorophyll cation radical and reduced plastocyanin. The fraction of chlorophyll triplet which is quenched by oxidized plastocyanin increases, and the yield of electron transfer products also increases, with an increase in the magnitude of the positive charge on the vesicles. Product decay and rise halftimes decrease with an increase in the mole percent of DODAC+ incorporated into egg phosphatidylcholine vesicles. However, both of these halftimes are independent of oxidized plastocyanin concentration. Even though ∼50% of the Chi triplets were quenched, no electron transfer product formation was observed in 5 mM phosphate buffer (pH=7.0). Under similar conditions in betaine, approximately 13% of the Chi triplets could be converted into products.
MITOCHONDRIAL PHOTOSENSITIZATION BY PHOTOFRIN II
Authors: Singh Gurmit , Jeeves W. Patrick , Wilson Brian C. , Jang Daniel
Published: January 2008

Abstract V‐79 Chinese hamster cells grown as monolayers or as multicell spheroids were treated with Photofrin II (10 μ.g m−1 for 16 h) and various doses of red light irradiation. The resulting biochemical and functional damage to cell mitochondria was studied. The activities of both succinic dehydrogenese and cytochrome c oxidase were found to decrease in a light dose‐dependent manner. The respiratory control quotient (RC) decreased in parallel with a decrease in the activities of the respiratory chain proteins. Our data also showed a distinct temporal difference in the relative progression of mitochondrial damage and cell death as assessed by loss of discrete Rhodamine‐123 (Rh‐123) localization and trypan blue infiltration, respectively. Mitochondrial damage was detected immediately, as seen by derealization of Rh‐123 resulting from dissipation of the electrochemical gradient in damaged mitochondria. Trypan blue infiltration occurs with a distinct time lag. These findings are consistent with the hypothesis that, at least for long Photofrin II incubation times, the mitochondrion is a primary target of photosensitization. The subsequent changes in cell membrane permeability may be a delayed result of decreased bioenergetics of the Photofrin II photosensitized cell.
PHTHALOCYANINE PHOTOSENSITIZATION FOR IN VITRO ELIMINATION OF RESIDUAL ACUTE NON‐LYMPHOBLASTIC LEUKAEMIA: PRELIMINARY EVALUATION
Authors: Singer C. R. J. , Bown S. G. , Linch D. C. , Huehns E. R. , Goldstone A. H.
Published: January 2008

Abstract Autologous bone marrow transplantation (ABMT) in first remission of acute non‐lympho‐blastic leukaemia (ANLL) has increased the proportion of patients eligible for intensive myeloablative therapy and has produced encouraging early results. However, more patients relapse after ABMT than after allogeneic BMT and this may be due in part to reinfusion of leukaemia with the graft. We have examined the phototoxicity of sulphonated chloro‐aluminium phthalocyanine (SPC) on leukaemic blasts from patients with ANLL and normal myeloid progenitors (GM‐CFC) to determine whether in vitro phototherapy might be used to eliminate residual ANLL from bone marrow grafts. ANLL blasts were shown to take up SPC readily and the phototoxicity was shown to be dependent on the concentration of SPC, duration and temperature of incubation, the interval from SPC incubation to light exposure and the duration of light exposure using 675 nm light delivered by an optical fibre at 50 mV from an Ar pumped dye laser. After a 2 hour incubation at 25 μ.g SPC m−1 recovery of ANLL blasts at 24 h was 5 ± 2% whilst GM‐CFC recovery from normal marrow was 47 ± 9%. This study suggests that ANLL blasts may be more sensitive to SPC phototoxicity than normal marrow GM‐CFC, and further studies to examine the potential of this compound for the elimination of residual ANLL from marrow autografts are in progress.
In vivo 31P‐NMR SPECTROSCOPY OF MAMMARY CARCINOMA SUBJECTED TO SUB CURATIVE PHOTODYNAMIC THERAPY
Authors: Chopp M. , Farmer H. , Hetzel F. , Schaap A. P.
Published: January 2008

Abstract In vivo
31P‐NMR spectroscopy was applied to the investigation of the time course of metabolic response of MCA mammary carcinoma in the C,H mouse subjected to a subcurative treatment with photodynamic therapy. Eleven animals were injected with 12.5 mg kg_1 Photofrin II and after 24 h were photoactivated with 25 J cm−2 of light between 630 ± 5 nm. In vivo NMR spectroscopy was performed 1‐4, 24 and 72 h after treatment. The ratio of (J‐ATP intensity to inorganic phosphate (Pi) intensity changed over the time course of the study. At the 1‐4 and 24 h time points the ratio of fi‐ATP to Pi decreased from control values. At 72 h there was a significant increase in the ratio above the post treatment values to levels equal to or exceeding that of control pretreatment ratios.
MORPHOLOGICAL CHANGES OF TUMOR MICROVASCULATURE FOLLOWING HEMATOPORPHYRIN DERIVATIVE SENSITIZED PHOTODYNAMIC THERAPY*
Authors: Chaudhuri Kallol , Keck Rick W. , Selman Steven H.
Published: January 2008

Abstract There is increasing evidence that the tumor microvasculature is affected during porphyrin photodynamic therapy. In the following study, the effect of hematoporphyrin derivative photodynamic therapy on tumor microvasculature was studied by electron microscopy. Urothelial tumors, implanted subcutaneously in rats, were exposed to red light (> 590 nm; 360 J cm−2) 72 h after injection of hematoporphyrin derivative at a dose of 5 mg kg−1 of body weight. Prior to sampling, in vivo perfusion was carried out using a polyvalent cation, lanthanum, in 3% glutaraldehyde to define the endocapillary layer of endothelial cells. Samples of tumors were collected at 0, 1,2 and 4 h after completion of photodynamic therapy. Histological changes in endothelial cells were evident immediately following completion of light exposure. Immediate morphological changes included absence of the endocapillary layer as well as mitochondrial degeneration. The changes within tumor cells followed the changes within the microvasculature. This study indicates that the endothelial cell of tumor tissue is an important target of photodynamic therapy and may be responsible for the blood flow changes reported previously.
TUMOR DESTRUCTION IN PHOTODYNAMIC THERAPY
Authors: Nelson J. Stuart , Liaw L.‐H. , Berns Michael W.
Published: January 2008

Abstract The effects of photodynamic therapy (PDT) on the tumor microvasculature in the first few hours after treatment was studied at the light microscope (LM) and electron microscope (EM) levels in DBA/2Ha mice bearing SMT‐F tumors. Animals received intraperitoneal injections of 10 mg kg− of Photofrin II and 24 h later tumors were treated with 100 J cm−2 of light (630 nm). Animals were sacrificed and their tumors removed at time 0, 30 min, 1, 2, 4, 8, 16 and 24 h after treatment. The results indicate that the effects of PDT are initially direct destruction of the microfibrils in the subendothelial zone of the tumor capillaries with subsequent tumor cell death secondary to hemorrhage and vascular collapse.
PHOTODYNAMIC THERAPY OF HEAD and NECK SQUAMOUS CELL CARCINOMA: OPTICAL DOSIMETRY and CLINICAL TRIAL
Authors: Grossweiner Leonard I. , Hill James H. , Lobraico Rocco V.
Published: January 2008

Abstract This paper reports the retrospective comparison of a PDT dosimetry model with the current results of an ongoing clinical trial on photodynamic therapy (PDT) for head and neck squamous cell carcinoma (HNSCC). The model is based on the assumption that tumor eradication requires a minimum absorption of radiant energy by the tumor‐localized porphyrins. The diffusion approximation was employed to calculate the incident light dose required to attain the minimum absorbed energy density at tumor boundaries most distant from the light source. Dosimetry tables for HNSCC were calculated with estimated tissue parameters, giving the PDT light dose for front surface exposure (FS) and illumination by interstitial cylindrical diffuser fibers (CI) in terms of the tumor dimensions. The model includes a correction for the photobleaching of the localized photosensitizer by the therapeutic light. The PDT trial was carried out on nine patients with previously untreated or recurrent early stage tumors and one patient with a recurrent advanced stage tumor. A complete response was obtained in 83% (10/12) of the sites treated. The calculated doses for FS and CI exposures vary from comparable with to three‐fold lower than the actual doses for each complete response tumor site.
THE EVOLUTION OF PHOTODYNAMIC THERAPY TECHNIQUES IN THE TREATMENT OF INTRAOCULAR TUMORS
Authors: Murphree A. Linn , Cote Mary , Gomer Charles J.
Published: January 2008

Abstract The techniques of photodynamic therapy (PDT) and the indications for its use in the treatment of intraocular tumors have evolved during the years in which it has been assessed in patients at our institution. It is now clear that transcorneal PDT delivered at a subthermal dose‐rate to the surface of a pigmented lesion such as choroidal melanoma has little effect. In the absence of pigment, however, as in the case of retinoblastoma or amelanotic melanoma of the iris or choroid, the tumor kill attributed to PDT alone is significant. Data from animal tumor models in our institution and from patient studies elsewhere suggest that the addition of heat with the light delivery will predictably improve the outcome of the treatment of pigmented lesions. Ocular PDT delivered in conjunction with heat will be useful clinically as an adjunct to scleral plaque therapy by reducing the height of a lesion and concurrently the dose of radiation necessary at the base of the tumor for sterilization. Since the clinical tumoricidal effect of PDT is now known to be due at least in part to vascular damage, trans‐scleral application of light to the base of melanomas and occlusion of its blood supply holds significant promise of efficacy with continued improvement of the light delivery system. Finally, a transpupillary approach to occlusion of the choroidal vascular supply to a melanoma by surrounding the tumor with photodynamic lesions may provide the best approach for ocular PDT as a primary therapy.
SKIN PHOTOSENSITIVITY: DURATION and INTENSITY FOLLOWING INTRAVENOUS HEMATOPORPHYRIN DERIVATES, HpD and DHE
Authors: Razum Nicholas , Balchum Oscar J. , Profio A. Edward , Carstens Felix
Published: January 2008

Abstract In this pilot study, the duration and degree of skin photosensitivity after intravenous injection of HpD or DHE was tested sequentially once a week, using a solar simulator delivering 19.5 ± 1.5 J cm−2 to an area of skin 1.4 cm diameter. The longest duration of skin photosensitivity was 7 weeks amongst the 12 patients studied. In 180 other patients, the incidence of sunburn following PDT was less than 10% over a period of 7 y. Sunburn was always minimal (mild redness and swelling–no blisters), and required no systemic therapy or hospitalization. The reaction subsided within 2‐3 days. The low incidence was attributed to good verbal and written instructions in methods of prevention delivered to not only patients, but spouse, family members and friends by the investigator.
PHOTODYNAMIC THERAPY OF MALIGNANT PRIMARY BRAIN TUMOURS: CLINICAL EFFECTS, POSTOPERATIVE ICP, and LIGHT PENETRATION OF THE BRAIN
Authors: Muller Paul J. , Wilson Brian C.
Published: January 2008

Abstract We are reporting our experience with intraoperative PDT in 32 patients with malignant supratentorial gliomas; in 19 cases the tumour was recurrent. There were 20 males and 12 females with an age range of 17‐73 (mean = 45) yr. The first 8 patients in this series received HpD (Photofrin I) and the next 24 received DHE (Photofrin II). A photo‐illuminating device, of the author's design, was coupled to an argon dye pump laser in order to deliver light at 630 nm to a tumour cavity created by radical tumour resection and/or tumour cyst drainage. The total light energy delivered ranged from 440 to 3888 J and the light energy density ranged from 8 to 68 J cm−2.

There were two post‐operative deaths as the consequence of hematoma accumulation in an extensive tumour resection cavity. In two patients neurological function was worse post‐operatively and did not recover. Post‐operative cerebral edema was pronounced in eight cases and required emergency craniotomy in two patients (the histology from both showed hemorrhagic necrosis of residual tumour). We have fashioned continuous post‐operative ICP measurements in the last 15 patients treated with PDT and compared the values to those obtained from cases with malignant gliomas who did not have PDT; the mean ICP was significantly greater in the PDT group. Four patients developed wound infections; two of these required surgical treatment. Four patients, two of whom were hemiparetic, developed deep vein thrombosis and required anticoagulant therapy. There were no adverse systemic reactions to the administration of either photosensitizer and only 3 skin photosensitivity reactions.

Follow up has ranged from 1 to 26 months at the time of writing; 38% were still alive; in the interval between PDT and death, the deaths per observation year was 1.11 for the whole group and 1.00 when the two post‐operative deaths are excluded. In the interval between first diagnosis and death the rate was 0.45 deaths per observation year. Photodynamic therapy of malignant brain tumours using surface or cavitary photo‐illumination can be carried out with acceptable risk.

In eight patients we determined the penetration depth of light in brain tissue in vivo by reading the detected light flux from a fiber passed radially into the brain towards the centre of the irradiation volume. The optical fiber consisted of a single 400 μ.m, cleaved fiber fixed in a 17‐gauge biopsy needle coupled to a photometer. The light penetration depth ranged from 0.8 to 4.9. The mean PD values in the‘tumour’group and the‘brain’group was 2.9 ± 1.5 and 1.5 ± 0.43, respectively. We attribute this significant difference to the differences in the absorption and scattering properties of brain and tumour.
THE EFFECT OF SUBSTITUENTS ON PHTHALOCYANINE PHOTOCYTOTOXICITY
Authors: Rosenthal I. , Ben‐Hur E. , Greenberg S. , Concepcion‐Lam A. , Drew D. M. , Leznoff C. C.
Published: January 2008

Phthalocyanine (Pc) dyes are a class of photosensitizers that are being considered for use in the photodynamic therapy of cancer. A final choice for the most useful drug demands phototoxicity screening of various structurally related Pc dyes, such as those with different substituents at the peripheral benzene rings. Using the colony forming ability of Chinese hamster cells as an endpoint, the photobiological activity for ZnPc was found to be the highest for the unsubstituted compound, followed in decreasing order by the 2,9,16,23‐tetrahydroxy‐, 2,9,16,23‐tetrasulfonated‐, and 2,9,16,23‐tetraneopentoxy‐Pc derivatives. This effect could be correlated with the uptake rate of the respective Pc derivatives by the cells, but it is unrelated to the apparent lipophilicity of these compounds, or, alternatively, to their ability to photogenerate singlet oxygen. The first synthesis of a metal‐free tetrahydroxy Pc is described.
PHOTOREACTION OF MONOFUNCTIONAL 3‐CARBETHOXYPSORALEN WITH DNA: IDENTIFICATION AND CONFORMATIONAL STUDY OF THE PREDOMINANT cis‐syn FURAN SIDE MONOADDUCT TO THYMINE
Authors: Gaboriau F. , Vigny P. , Cadet J. , Voituriez L. , Bisagni E.
Published: January 2008

The main DNA‐3‐CPs furan side adduct has been isolated following acidic hydrolysis of photomodified DNA and subsequent reversed‐phase high performance liquid chromatography purification. This photoadduct has been identified as a thymine‐3‐CPs C4‐cycloadduct Thy<5 4′6 5′, >3‐CPs based on its optical spectroscopic features and of its plasma desorption mass spectrometric characteristics. Moreover, its reversed‐phase high performance liquid chromatography retention time is in agreement with a cis‐syn stereochemistry as compared to the chromatographic properties of the cis‐syn model adduct Thy< 5 4′6 5′ >3‐CPs previously identified. Further support for the cis‐syn stereoconfiguration assignment was provided by fluorescence quenching experiments using iodide and silver ions as external and internal quenchers respectively. These data strongly indicate that the Thy< 5 4′6 5′ >3‐CPs photoadduct is located inside the DNA helix in agreement with its cis‐syn stereochemistry.
KINETICS AND MECHANISM OF CATALYSIS BY FERRIHAEMS IN THE CHEMILUMINOGENIC OXIDATION OF LUMINOL BY HYDROGEN PEROXIDE
Authors: Jones Peter , Scowen Nina R.
Published: January 2008

The kinetics of catalysis by deuteroferrihaem (deuterohaemin) were studied in the chemiluminogenic oxidation of luminol by hydrogen peroxide. The results imply that two distinct catalytic mechanisms operate to yield chemiluminescence from excited aminophthalate emitter in this system. The first mechanism involves initial one‐electron oxidation of luminol by an oxidised derivative of deuteroferrihaem with well‐established peroxidatic oxidant properties. The second mechanism involves a concerted pathway very similar to that which has been proposed [Olsson, T., L. Ewetz and A. Thore (1983), Photochem. Photobiol.38, 223–229] to explain protoferrihaem (haemin) catalysis in luminol oxidation. Deuteroferrihaem is a much more effective catalyst than protoferrihaem on a mole‐for‐mole basis and could be used with advantage in chemiluminescence analyses.
LATERAL INTERACTIONS BETWEEN VERTEBRATE PHOTORECEPTORS
Authors: Piccolino Marco , Trimarchi Carmela
Published: January 2008

Vertebrate photoreceptors generate electrical signals across their cell membrane when they absorb light. Recent studies show, moreover, that the membrane potential of an individual photoreceptor may be also modified by illumination of its neighbors. Two types of lateral interactions have been described: a direct interaction mediated by electrical synapses between adjacent photoreceptors, and a recurrent interaction mediated by a feedback circuit involving horizontal cells. In the first mechanism, photoreceptors summate their responses over short retinal distances. In the feedback circuit photoreceptors may develop light responses of opposite polarity to those induced by direct illumination. In general, these ‘antagonistic’ responses are best elicited by large area retinal illumination. As a consequence of these photoreceptor interactions rather complex processing of visual information, in both spatial and chromatic domains, occurs at the first stage of the retinal network.
PHOTOBLEACHING OF A CYANINE DYE IN SOLUTION AND IN MEMBRANES
Authors: Valdes‐Aguilera O. , Cincotta L. , Foley J. , Kochevar I. E.
Published: January 2008

Abstract— N,N′‐bis(2‐ethyl‐1,3‐dioxolane)‐kryptocyanine (EDKC), a lipophilic dye with a delocalized positive charge, photosensitizes cells to visible irradiation. In phosphate‐buffered saline (PBS), EDKC absorbs maximally at 700 nm (ε= 1.2 × 105 M−1 cm−1) and in methanol, the absorption maximum is at 706 nm (ε= 2.3 × 105 M−1 cm−1). EDKC partitions from PBS into small unilamellar liposomes prepared from saturated phospholipids and into membranes prepared from red blood cells (RBC) and binds to human serum albumin (HSA). The EDKC fluorescence maximum red shifts from 713 nm in PBS to 720–725 nm in liposomes and RBC membranes and the fluorescence intensity is enhanced by factors of 14–35 compared to PBS (φ= 0.0046). EDKC is thermally unstable in PBS (T1/2= 2 h at 1.3 × 10−5M EDKC), but stable in methanol. In liposomes and RBC membranes, EDKC is 10 times more stable than in PBS, indicating that it is only partially exposed to the aqueous phase. Quenching of EDKC fluorescence in liposomes and RBC membranes by trinitrobenzene sulfonate also indicates that EDKC is not buried within the membranes. Photodecomposition of EDKC was oxygen‐dependent and occurred with a low quantum yield (6.4 × 10−4 in PBS). Singlet oxygen was not detected upon irradiation of EDKC in membranes or with HSA since the self‐sensitized oxidation of EDKC occurred at the same rate in D2O as in H2O and was not quenched by sodium azide or histidine.
SELECTIVE ALTERATION OF THE PIGMENT COMPOSITION OF THE BLUE‐GREEN ALGA, Anacystis nidulans
Authors: Gombos Z. , Szalontai B. , Surányi Gy , Csatorday K.
Published: January 2008

Abstract— Conditions were established which allow selective alteration of the pigment composition of Anacystis cells. Nitrate‐starvation at 28°C and 39°C resulted in the preponderance of chlorophyll a (Chi a) and that of phycocyanin (PC). In the case of starvation at 39°C strong correlation was observed between the disappearance of Chi a absorption and the appearance of an absorption band at 750 nm (P750) as the starvation proceeded. During regeneration the starved cells lost their P750 content. We show that P750 is quantitatively accounted for in the form of Chi a aggregates.
CHEMILUMINESCENCE IN THE OXIDATION OF 6‐HYDROXYDOPAMINE: EFFECTS OF LUCIGENIN, SCAVENGERS OF ACTIVE OXYGEN, METAL CHELATORS AND THE PRESENCE OF OXYGEN
Authors: Fatur Dolores J. , San Richard H. C. , Davison Allan J. , Stich Hans F.
Published: January 2008

Abstract— Maximum chemiluminescence in a system containing 6‐hydroxydopamine (6‐OHDA) and H2O2 required the addition of Fe2+:EDTA, oxygen, and lucigenin. In this system luminescence was strongly inhibited by catalase (91% inhibition) or 50 mM mannitol (83%), whereas superoxide dismutase or ascorbate did not significantly change the reaction rate. In the absence of lucigenin, 50 mM mannitol (78%), catalase (76%), or ascorbate (73%) inhibited strongly, while superoxide dismutase inhibited by 60%. Removing EDTA from the lucigenin‐containing system caused a 79% decrease in luminescence, while the substitution of desferoxamine for EDTA decreased luminescence by 55%. In the presence of desferoxamine plus EDTA the luminescence increased by 30% in comparison with that seen with EDTA alone. Luminescence in the system containing 6‐hydroxydopamine, H2O2, Fe2+:EDTA and lucigenin required the presence of oxygen (93% inhibition anaerobically), consistent with a mechanism involving reductive oxygenation of the lucigenin. It is concluded that luminescence in the presence of lucigenin involves a substantial contribution from H2O2 and Fe2+ mediated by a mannitol‐sensitive intermediate (conceivably Fenton‐derived hydroxyl radicals). In the absence of lucigenin, superoxide and an ascorbate‐labile component are additional important participants in the process.
UROCANIC ACID PHOTOBIOLOGY. PHOTOCHEMICAL BINDING OF UROCANIC ACID TO BOVINE SERUM ALBUMIN*
Authors: Deibel R. M. , Morrison H. , Baird W. M.
Published: January 2008

Abstract— The photolysis of E‐[ring‐2‐14C]urocanic acid with bovine serum albumin (BSA) leads to incorporation of radiolabel into the protein. Levels up to 68 nmol mg−1 BSA have been observed if the irradiation is carried out in an inert atmosphere. Oxygen reduces the level slightly. It appears from gel‐filtration chromatography that the label incorporation is covalent in nature.
INACTIVATION BY MONOCHROMATIC NEAR‐UV RADIATION OF AN Escherichia coli hemA8 MUTANT GROWN WITH AND WITHOUT δ‐AMINOLEVULINIC ACID: THE ROLE OF DNA vs MEMBRANE DAMAGE
Authors: Peak Meyrick J. , Johnson Jennifer S. , Tuveson R. W. , Peak Jennifer G.
Published: January 2008

Abstract— Escherichia coli strain RT8 hemA8 [blocked in biosynthesis of δ‐aminolevulinic acid (δ‐ALA), and unable to manufacture porphyrins unless exogenously supplied with δ‐ALA] is inactivated more efficiently by monochromatic 334‐ and 405‐nm radiations if the cells are grown with δ‐ALA supplementation. The fiuence enhancement factor for δ‐ALA sensitization is larger for light at 405 nm than at 334 nm. Both irradiation conditions (plus or minus δ‐ALA) showed prominent oxygen enhancement ratios, which were also larger at 405 nm than at 334 nm. At 334 nm, δ‐ALA supplementation did not affect the accumulation of DNA breaks, while at 405 nm, the induction of DNA breaks doubled for cells supplemented with δ‐ALA. Rubidium leakage caused by 405‐nm radiation occurred at a smaller fiuence in cells supplemented with higher concentrations of δ‐ALA than in cells supplemented with a lower concentration. The results suggest that (1) porphyrin derivatives may have a role in cell killing by near‐UV radiations, and (2) damage to cytomembranes may be a critical lesion produced by these events, whereas DNA breakage may not.