bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF LIGHT AND TRITON X‐100 ON THE SIZE OF PROTOPLASTS FROM Ulothrix gigas
Authors: Davies Eric , Kuczmarski Dan 
Published: January 2008

Abstract— An electronic particle‐size analyzer (Coulter Counter with Channelyzer) was used both to monitor the purity of large numbers of protoplasts during sequential steps in their isolation from Ulothrix gigas and also to detect changes in volume (swelling or growth) after incubation of purified protoplasts under various conditions.Protoplasts almost devoid of contaminating debris, but heterogenous in size, were obtained by pelleting partly‐purified protoplasts through sucrose solutions. Pure protoplasts of discrete sizes were obtained by centrifuging these resuspended protoplasts on iso‐osmotic mannitol/sucrose gradients. The protoplasts were shown to enlarge (swell) and then burst when transferred to increasingly hypotonic solutions or when incubated in Triton X‐100.The rate of protoplast enlargement (growth) was also monitored on the Coulter Counter and differences in size of large populations were discernible within 2 h in protoplasts incubated under low light, and growth rates of such protoplasts could be assessed for up to 36 h.The Coulter Counter provides a rapid, reproducible and sensitive method for measuring the size distribution of large numbers of protoplasts. This, combined with the techniques described here for the isolation of protoplasts from V. gigas in high yield and purity, provides a system eminently suitable for investigating a wide array of physiological and developmental processes in plant protoplasts.
UV‐B EFFECTS ON TERRESTRIAL PLANTS
Authors: Tevini Manfred , Teramura Alan H. 
Published: January 2008

AbstractThe potential impacts of an increase in solar UV‐B radiation reaching the Earth's surface due to stratospheric ozone depletion have been investigated by several research groups during the last 15 years. Much of this research has centered on the effects of plant growth and physiology under artificial UV‐B irradiation supplied to plants in growth chambers or greenhouses. Since these artificial sources do not precisely match the solar spectrum and due to the wavelength dependency of photobiol‐ogical processes, weighting functions, based on action spectra for specific responses, have been developed to assess the biological effectiveness of the irradiation sources and of predicted ozone depletion. Recent experiments have also utilized artificially produced ozone cuvettes to filter natural solar radiation and simulate an environment of reduced UV‐B for comparative purposes.Overall, the effectiveness of UV‐B varies both among species and among cultivars of a given species. Sensitive plants often exhibit reduced growth (plant height, dry weight, leaf area, etc.), photosynthetic activity and flowering. Competitive interactions may also be altered indirectly by differential growth responses. Photosynthetic activity may be reduced by direct effects on photosynthetic enzymes, metabolic pathways or indirectly through effects on photosynthetic pigments or stomatal function. The fluence response of these changes has yet to be clearly demonstrated in most cases. Plants sensitive to UV‐B may also respond by accumulating UV‐absorbing compounds in their outer tissue layers, which presumably protect sensitive targets from UV damage. Several key enzymes in the biosynthetic pathways of these compounds have been shown to be specifically induced by UV‐B irradiation.Few studies have documented the effects of UV‐B on total plant yield under field conditions. One notable exception is a 6‐yr study with soybean demonstrating harvestable yield reductions under a simulated 25% ozone depletion. These effects are further modified by prevailing microclimatic conditions. Plants tend to be less sensitive to UV‐B radiation under drought or mineral deficiency, while sensitivity increases under low levels of visible light. Further studies are needed to understand the mechanisms of UV‐B effects and the interactions with present stresses and future projected changes in the environment.
FLUORESCENCE SPECTRA IN LUNG WITH PORPHYRIN INJECTION
Authors: ANTHONY D. J. , PROFIO A. E. , BALCHUM O. J. 
Published: January 2008

AbstractThe fluorescence emission spectra from human bronchial mucosa and tumors, before and after injection of dihematoporphyrin ether/ester, have been measured with an optical multichannel analyzer from 500 to 750 nm. Fluorescence was excited with a violet krypton ion laser (average wavelength 410 nm). The autofluorescence spectra decrease monotonically with increasing wavelength except for a small broad peak near 600 nm. The spectra from tumor sites, after injection of the fluorescent porphyrin, exhibit the characteristic fluorescence emission at 630 and 690 nm, added to the autofluorescence spectrum. The spectra from control or nontumor sites are similar but the magnitude of the component due to the injected porphyrin is smaller than at a tumor site. The magnitude ratio of tumor to control site fluorescence depends on concentration of the porphyrin, tumor thickness, and time after injection. Autofluorescence degrades contrast and thus makes very thin tumors difficult to image. Subtraction of the autofluorescence background is desirable.
THE STIMULATING EFFECT OF A COLD, DARK PRETREATMENT ON THE ETIOPLAST/CHLOROPLAST TRANSFORMATION OF ANGIOSPERMS–II. SYNERGISM BETWEEN RED‐LIGHT and COLD PRETREATMENT ON THE CO2‐ and O2‐GAS‐EXCHANGE OF WHEAT LEAVES
Authors: Schönbohm Ekkehard , Czeska‐Werner Ulrike 
Published: January 2008

Abstract— Recently we reported on the stimulating effect of a cold, dark pretreatment on the processes of greening of dark‐grown angiosperms under continuous white light (Schönbohm et al., 1988; Physiol. Plant.72,541–546). These effects could be nullified by a subsequent second dark phase (25°C) which precedes the white light period.Our analysis was now focused on the effect of cold, dark pretreatments (with or without red‐preirradiation) on the gas exchange (O2; CO2) of etiolated primary leaves of wheat during a subsequent white light period. The following results were obtained:(1) The net‐O2‐consumption under continuous white light decreased much more quickly after a cold than after a warm pretreatment.(2) This effect was enhanced by red‐preirradiation.(3) The O2‐compensation point was reached more quickly during the de‐etiolation period when the leaves had been subjected to a cold instead to a warm pretreatment.(4) The “cold‐effect” could be nullified by a subsequent warm, dark pretreatment (in this material the compensation point could not be reached within 8 h).(5) Cold treated material which had also been exposed to red light showed during the first 30 min of de‐etiolation an extremely strong “out‐burst” of CO2. No correlation was apparent between the O2‐uptake and this high CO2‐release.(6) A cold, dark pretreatment induces a decrease of CO2‐release during the second half of the de‐etiolation period. This effect could be nullified by a secondary warm, dark treatment given after the cold, dark pretreatment.Our experiments indicate that red‐preirradiation and cold, dark pretreatment stimulate chlorophyll synthesis (Schonbohm et al., 1988) and also photosynthetic O2‐evolution and CO2‐uptake. We also assume that this pretreatment causes CO2 release that is neither directly related to the respiratory electron transport chain nor to the photorespiration.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID BILAYER VESICLES: VECTORIAL ELECTRON TRANSFER ACROSS THE BILAYER FROM REDUCED CYTOCHROME c IN THE INNER COMPARTMENT TO OXIDIZED FERREDOXIN IN THE OUTER COMPARTMENT
Authors: Zhao Zhan‐Gong , Tollin Gordon 
Published: January 2008

AbstractA negatively charged large unilamellar vesicle system containing a membrane‐bound photo‐sensitizer (chlorophyll, Chi), a reduced redox protein [cytochrome c, cyt c(red)] in the inner aqueous compartment, an oxidized redox protein [ferredoxin, Fd(ox)] in the outer aqueous compartment, and propylene diquat (PDQ2+) as a mediator, was investigated using both flash and steady‐state photolysis techniques. The results demonstrate that the light‐generated triplet state of Chi (3Chl) was initially quenched by PDQ2+ at the outer membrane surface to form Chi cation radical (Chl+) and the reduced diquat (PDQ+). This was succeeded by a biphasic recombination between Chi+ and PDQ+. The slow phase of the recombination process, which represents reverse electron transfer between Chl+ and those PDQ+ molecules which escaped from the membrane surface, could be suppressed effectively both by the reduction of Chl^ in the inner monolayer of the vesicles by cyt c(red), and by the reoxidation of PDQ+ by Fd(ox) in the outer aqueous compartment. These reactions lead to the permanent accumulation of oxidized and reduced product proteins, i.e. cyt c(ox) in the inner compartment and Fd(red) in the outer compartment. The yields of such accumulation were 11%, based on the 3Chl quenched, and 1.4%, based on absorbed quanta, under the conditions used in the present study. This system mimics one of the key events in natural photosynthesis and results in an appreciable storage of electromagnetic energy in the reaction products.
DEMONSTRATION THAT PHOSPHORESCENT 6‐BROMO‐2‐NAPHTHYL SULFATE CAN BE USED TO PROBE HEME ACCESSIBILITY IN HEME PROTEINS
Authors: Bayles Stephen W. , Beckham Suzy , Leidig Paige R. , Montrem Anne , Taylor Mervin L. , Wright Tony M. , WU Ying , Schuh Merlyn D. 
Published: January 2008

AbstractThe phosphorescence properties of 6‐bromo‐2‐naphthyl sulfate (BNS) in aqueous solution were studied. The phosphorescence lifetime is several hundred us and is self‐quenched. Although a fluorescent photoproduct is formed from BNS, it does not interfere with the decay properties of triplet‐state BNS and its utility as a probe of the accessibility of the heme group in heme proteins. Quenching of BNS phosphorescence does not occur for the non‐heme protein lysozyme and apomyoglobin but occurs by a dynamic mechanism with a quenching constant of1–2 × 109M−1 s−1 for cytochrome c and myoglobin and with a quenching constant of 6.2 × 109M−1 s−1 for protoporphyrin IX. The phosphorescence of an inclusion complex of 1‐bromonaphthalene and β‐cyclodextrin is not quenched by heme‐containing proteins. The temperature and viscosity dependencies of the rate with which BNS phosphorescence is quenched by microperoxidase‐11 are consistent with unit quenching efficiency. These results indicate that quenching of BNS phosphorescence occurs only upon contact with the quencher, and the quenching constant can be used to assess the degree of accessibility of the heme group.
SUBNANOSECOND SINGLE PHOTON TIMING MEASUREMENTS USING A PULSED DIODE‐LASER*
Authors: Farrens David L. , Song Pill‐Soon 
Published: January 2008

AbstractThe convenient and inexpensive use of a pulsed diode‐laser (Hamamatsu Photonics PLP‐01 660 nm) is demonstrated as a low cost alternative to a standard pulsed laser or gas discharge flash system in a commercial time‐correlated single photon counting instrument. Fluorescence lifetimes of compounds of photobiological interest such as phytochrome, chlorophyll a, 1,1 ′‐diethyl‐4,4′ carbocyanine iodide (DCI/cryptocyanin),5,10,15,20‐tetra(p‐phenyl) porphyrin and stentorin I are presented using the pulsed diode‐laser source.
EFFECTS OF SOLAR RADIATION ON MOTILITY IN: Stentor coeruleus
Authors: Häder Donat‐P. , Häder Maria A. 
Published: January 2008

AbstractThe effects of solar radiation on the motility of the colored ciliate, Stentor coeruleus, have been assessed as a photodynamic model system for hypericism. The organism has been found to be extremely sensitive to solar radiation–a few minutes of unfiltered radiation suffice to arrest motility and decrease the velocity of movement. Removing UV‐B and UV‐A radiation prolongs the tolerated exposure times. From the present study, the mechanisms of the photodynamic action in S. coeruleus and in hypericin‐sensitized reactions have not been resolved in terms of Type I and II mechanisms.
PHOTOLYSIS OF DIBENZYLKETONES IN SUPERCRITICAL ETHANE and CARBON DIOXIDE*
Authors: O'Shea Kevin E. , Combes James R. , Foxt Marye Anne , Johnston Keith P. 
Published: January 2008

AbstractThe Norrish Type I photofragmentation of two dibenzylic ketones (l,3‐diphenyl‐2‐pro‐panone and l‐(4‐methylphenyl)‐3‐phenyl‐2‐propanone) in supercritical ethane and carbon dioxide proceeds without evidence for cage recombination of the photogenerated radical pair. A statistical mixture of the bibenzyls formed by random coupling of benzyl and p‐xylyl radicals was observed and the first order rate constant for the depletion of the reactant was independent of pressure. These results indicate that solvent cage effects are not operative in these low viscosity supercritical fluids even in the near critical region where solute‐solvent clustering is presumably maximal.
STRUCTURAL ELUCIDATION OF THE 8‐METHOXYPSORALEN OXIDIZED PRODUCT THAT INHIBITS THE CHEMOTACTIC ACTIVITY OF POLYMORPHONUCLEAR NEUTROPHILS TOWARD ANAPHYLATOXIN C5a
Authors: Mizuno Nobuyuki , Esaki Kenji , Sakakibara Jinsaku , Murakami Nobutoshi , Nagai Shinichi 
Published: January 2008

AbstractThe chemical structure of the 8‐methoxypsoralen oxidized product that inhibits the chemo‐tactic activity of anaphylatoxin C5a was determined to be 2,3‐dihydro‐2,9‐dimethoxy‐3‐hydroxy‐7‐oxo‐7H‐futo[3,2‐g][l]benzopyran. Its minimal concentration required to obtain the maximum inhibition of C5a des Arg (1 times 10−8M) chemotactic activity is 2.5 times 10−8M. Bioactivity of this substance was maintained for 2 weeks, stored in a dark room at room temperature under aerobic conditions. There is a possibility that this substance may be useful in the treatment of immune complex diseases.
EFFECTS OF LIGHT BEAM SIZE ON FLUENCE DISTRIBUTION AND DEPTH OF NECROSIS IN SUPERFICIALLY APPLIED PHOTODYNAMIC THERAPY OF NORMAL RAT BRAIN
Authors: Chen Qun , Wilson Brian C. , Dereski Mary O. , Patterson Michael S. , Chopp Michael , Hetzel Fred W. 
Published: January 2008

Abstract—The light fluence distributions of 632.8 nm light incident on the exposed surface of normal rat brain in vivo have been measured using an interstitial, stereotactically‐mounted optical fiber detector with isotropic response. The dependence of the relative fluence rate on depth and the spatial distribution of fluence were compared for incident beam diameters of 3 and 5 mm. The fluence rate at depth of 1–6 mm along the optical axis within the brain tissue was approximately 70% greater for a 5 mm diameter beam than for a 3 mm beam, at the same incident fluence rate, although the plots of the relative fluence rate vs depth were parallel over the depth range 1–6 mm. The depths of necrosis resulting from photodynamic treatment of brain tissue using the photosensitizer Photofrin and irradiation by 632 nm light with 3 and 5 mm incident beams were also measured. The observed difference in necrosis depths was consistent with the measured difference in fluence. The importance of beam size in photodynamic treatment with small diameter incident light fields is discussed.
THE HAIRLESS MOUSE MODEL OF PHOTOAGING: EVALUATION OF THE RELATIONSHIP BETWEEN DERMAL ELASTIN, COLLAGEN, SKIN THICKNESS AND WRINKLES
Authors: Moloney Stephen J. , Edmonds Susan H. , Giddens Lori D. , Learn Douglas B. 
Published: January 2008

Abstract—Quantitative and qualitative changes in dermal collagen and elastin occur in response to chronic ultraviolet (UV) irradiation. These changes have been implicated in the genesis of the wrinkling seen in chronically irradiated, or photoaged skin. We examined the relationship between wrinkle formation and changes in dermal structural protein content and type. Skh‐1 hairless mice were irradiated with suberythemal doses of UV‐B three times a week for up to 20 wk. Visible wrinkling was present after 6–7 wk of irradiation. Dermal elastic fiber content was quantified by color image analysis of paraffin‐embedded tissue. There was no significant difference in dermal elastic fiber content between irradiated and age‐matched control mice after either 10 or 20 wk of irradiation. The effect of UV‐B irradiation on total dermal collagen content, ratio of collagen type III‐type I, and extent of glycosylation and crosslinking of collagen was no different in irradiated and age‐matched control mice after 10 wk of irradiation. Increased epidermal thickness was evident in frozen sections after 6 wk of irradiation, and the thickness increased with continued irradiation. Dermal thickening was evident after 10 wk of irradiation. Sufficient UV‐B irradiation will eventually cause changes in dermal elastin and collagen content; however, wrinkle formation precedes such changes. A causal relationship between wrinkle formation and dermal structural protein content changes in Skh‐1 hairless mice could not be established in this study.
CHEMIEXCITATION IN THE PEROXIDATIVE METABOLISM OF DIETHYLSTILBESTROL. METABOLIC PRODUCTS
Authors: Knudsen Fernanda da Silva , Cilento Giuseppe 
Published: January 2008

Abstract— In the presence of the surfactant hexadecyltrimethyl ammonium bromide (CTAB) a cascade of electronically excited states accompanies the successive steps in the peroxidative metabolization of the strong estrogenic and tumourogenic diethylstilbestrol. Reversing the order by necessity, we report in this first paper results with the metabolites.Exposure of 4‐hydroxypropiophenone, Z, Z‐dienestrol or E, E‐dienestrol to horseradish peroxidase and H2O2 promotes oxygen uptake and spectral alterations. Light emission is observed provided that the surfactant CTAB is present. With the three substrates, 4‐hydroxybenzoic acid and a new metabolite, p‐benzoquinone, have been identified. With both dienestrol isomers, 1‐(4'‐hydroxyphenyl)‐propan‐1‐on‐2‐ol has been identified.In all cases the emission spectrum indicates the presence of several emitters. Possible chemiexcitation routes are pointed out. From the dramatic increase of the emission by enhancers, values as high as 1 × 10‐5 are inferred for the product of the quantum yields of chemiexcitation and energy transfer.
REDOX REGULATION OF ENERGY TRANSFER EFFICIENCY IN ANTENNAS OF GREEN PHOTOSYNTHETIC BACTERIA
Authors: Blankenship Robert E. , Cheng Peiling , Causgrove Timothy P. , Brune Daniel C. , Wang Stephanie Hsiao‐Hsien , Choh Jin‐Ug , Wang Jian 
Published: January 2008

AbstractThe efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane‐bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is ‐146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range7–10. Extraction of isolated chlorosomes with hexane has little effect on the redox‐induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water‐soluble bacteriochlorophyll a‐containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide‐induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.
SPECTROSCOPIC PROPERTIES OF THE POTENTIOMETRIC PROBE MEROCYANINE‐540 IN SOLUTIONS AND IN LIPOSOMES
Authors: Ehrenberg Benjamin , Pevzner Eliyahu 
Published: January 2008

AbstractAbsorption, fluorescence and resonance Raman spectra of the membrane dye merocyanine‐540 (MC540) were measured. The aggregation of the dye, its binding to lipid membranes and its response to crossmembrane electric potential differences were studied. The dye was found to aggregate even at micromolar concentrations in water, but not in organic solvents. The dimerization constant was evaluated by spectroscopic techniques. The binding constant to liposomes was estimated by a spectroscopic titration method. Resonance Raman spectra of MC540 were measured for the first time. Distinct changes were observed in the vibrational spectrum upon the generation of a valinomycin‐induced K+ diffusion potential (Nernst potential) on liposomes. The ratio of Raman band intensities, which was found to be related to the membrane potential, can be used to evaluate the absolute value of the electric potential.
DEVELOPMENT OF AN in vitro SYSTEM FOR THE ANALYSIS OF ULTRAVIOLET RADIATION‐INDUCED SUPPRESSION OF NATURAL KILLER CELL ACTIVITY
Authors: Hersey Peter , Magrath Helene , Wilkinson Frank 
Published: January 2008

AbstractPrevious studies have shown that natural killer (NK) cell activity was suppressed in volunteer subjects exposed to ultraviolet radiation (UVR) from solarium lamps. The present studies were carried out to determine that spectrum of UVR responsible for suppression of NK activity and to develop in vitro methods to analyze the effectivenes of sunscreen agents in prevention of UVR‐mediated suppression of NK activity and other aspects of immune function. UVR from a xenon are lamp source was used to irradiate peripheral blood lymphocytes (PBL) in wells of tissue culture flasks, and transmission interference filters were used to eliminate UVR of particular wavelengths. The results indicated that UVR from this source inhibited NK activity of PBL in a dose‐dependent manner with a 50% inhibitory dose of 5.5 mJ/cm2 when unfiltered and 29.6 mJ/cm2 when diluted through cellulose acetate, which gave a UV spectrum similar to that in solar radiation. Equivalent suppression of NK activity was mediated by UV‐A (UVR > 315 nm) at dose levels of 4.2 J/cm2, which was approximately 140 times greater than the amount of UV‐B (UVR > 315 nm) needed to suppress NK activity. Similar dose‐response curves were seen for inhibition of mitogenic responses to phytohemagglutinin except that the latter appeared less sensitive than NK to inhibition by UV‐A. These studies suggest that whe the greater proportion of UV‐A in solar radiation adn its greater penetration into skin is taken into account, UV‐A may have equivalent or greater direct immunosuppressive effects than UV‐B. The mechanisms of their immunosuppressive effects may, however, differ. The in vitro system described here would appear to provide a simple test system for further analysis of UVR‐indued imunosuppression.
THE ROLE OF LIPOPROTEINS IN THE DISTRIBUTION OF TIN ETIOPURPURIN (SnET2) IN THE TUMOR‐BEARING RAT
Authors: Kessel David , Garbo Greta M. , Hampton James 
Published: January 2008

AbstractThe role of plasma lipoproteins in the distribution of the photosensitizing agent tin etiopurpurin (SnET2) was examined in male rats bearing the N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide‐induced tumor. Treatement with 17α‐ethinyl estradiol resulted in the depletion of total plasma cholesterol by > 70% and a corresponding decrease in plasma lipoproteins. To both control and estradiol‐treated animals, a therapeutic dose (1.5mg/kg) of SnET2 was administered and biodistribution measured 24 h later. Estradiol treatment was not associated with difference in the distribution of SnET2 to liver, skin or tumor, or in the pattern of affinity of SnET2 to plasma albumin and lipoprotein. These results indicate that a substantial decrease in circulating lipoprotein levels does not alter patterns of SnET2 biodistribution.