bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTODYNAMIC THERAPY OF NORMAL CEREBRAL TISSUE IN THE CAT: A NONINVASIVE MODEL FOR CEREBROVASCULAR THROMBOSIS
Authors: Chopp Michael , Glasberg Mark R. , Riddle Jeanne M. , Hetzel Fred W. , Welch K. M. A. 
Published: January 2008

Abstract The early neuropathological response of normal cat brain to photodynamic therapy was investigated. Photofrin II was injected (IV) into a cat and photoactivated with red light from a filtered incandescent lamp. Animals were subjected to phototherapy either through the intact skull or with energy deposition onto the intact dura. Following photoactivation the animals were maintained for 6 h after which time the brain was removed and sections submitted for electron microscopic and or light microscopic study.Gross anatomical analysis of the photoactivated brain revealed hemorrhagic dusky discoloration limited to the area of the tissue illuminated. Animals that failed to show a lesion were cats characterized by low Photofrin II dosage and low photoactivation intensity. The microscopic cortical features of cats with lesions included prominent capillary congestion and regions of marked vacuolization and rarefaction. Blood vessels were structurally altered and the lumen of many vessels was completely filled with tightly packed erythrocytes. Our study suggests that the acute neuropathological response of cerebral tissue to photoactivation resembles that of microvascular thrombosis. It is thus reasonable to explore PDT of normal tissue as a non invasive model of cerebrovascular thrombosis in the cat.
POTENTIAL INVOLVEMENT OF FREE RADICAL REACTIONS IN ULTRAVIOLET LIGHT‐MEDIATED CUTANEOUS DAMAGE*
Authors: Black Homer S. 
Published: January 2008

AbstractFree radicals are chemical species characterized by an odd number of orbital electrons or by pairs of electrons of similar directional spin isolated singly in separate orbitals. Consequently most of these agents are highly reactive and usually exhibit an extremely short half‐life, although due to steric and resonance effects some exceptions occur. Some radicals and their precursors, such as the diradical O2 which exists in the triplet state, represent a critical and essential element of normal metabolism of aerobic organisms where, under normal circumstances, controlled reduction of reactive oxygen species occurs via the cytochrome oxidase or cytochrome P‐450 mixed function monooxygenase systems. In addition to reactive oxygen species, organisms may be subjected to a wide‐range of other free radicals or their precursors, including those of both exogenous and endogenous origin. Elaborate defense mechanisms have evolved to avoid cellular damage from these highly reactive species. Enzymes, such as the superoxide dismutase, the glutathione peroxidase/reductase system, and catalase; interactions with conjugated diene systems such as those found in melanins, carotenoids, and tocopherols; and direct reduction by sulphydryl compounds, phenols, and purines represent but a few of these natural defense systems.Despite a strong rationale for considering free radicals as pathologic agents, progress in implicating these agents, or their reactions, in pathologic processes has been arduous. The fore‐most hurdle to providing definitive evidence for free radical involvement rests with the highly transient nature of these species, hardly reaching measurable levels in vivo and thereby making rigorous testing of the hypothesis extremely difficult. Indeed, free radical damage has been studied, for the most part, by indirect means–usually by measurement of known free radical reaction intermediates and products from which free radical involvement is implied. Nevertheless, free radical formation has been shown to occur in UV‐irradiated skin and a considerable body of circumstantial evidence has been amassed that strongly infers that these agents, or reactions initiated by them, are responsible for at least some of the deleterious effects of UV upon skin.
NEAR‐INFRARED DETECTION OF SINGLET MOLECULAR OXYGEN PRODUCED BY PHOTOSENSITIZATION WITH PROMAZINE and CHLORPROMAZINE
Authors: Hall Robert D. , Buettner Garry R. , Moiten Ann G. , Chignell Colin F. 
Published: January 2008

AbstractA sensitive near‐infrared detection system has been used to study the steady‐state emission of 1O2 at 1268 nra produced by promazine (PZ) and chlorpromazine (CPZ) during photo‐illumination. Singlet molecular oxygen could be detected in a variety of ordinary and perdeuterated organic solvents, but was not detectable in water or deuterium oxide. The emission was enhanced in the perdeuterated organic solvents and could be eliminated by rigorous degassing or by addition of the singlet oxygen scavenger 2,3‐dimethylfuran. Singlet oxygen could not be detected in any of the solvents during irradiation of the sulfoxides of PZ and CPZ. We conclude that in biological systems 1O2 production is not a major pathway to phototoxicity for the sulfoxides, while for the parent phenothiazines the formation of 1O2 is much more likely to be important in nonpolar environments such as cell membranes than in the aqueous parts of the cell.
THE EFFECT OF PORPHYRIN PHOTOSENSITIZERS ON THE TOXICITY OF l,3‐BIS(2‐CHLOROETHYL)‐1‐ NITROSOUREA IN C57BL/6J MICE
Authors: Muller P. J. , Wilson B. C. , Chada K. 
Published: January 2008

Abstract The most widely used agents for photodynamic therapy are the porphyrin photosensitizers. It has been shown that hematoporphyrin derivative (HpD) can cause murine marrow hypercellularity and splenic hypertrophy. We have examined the effect on survival and marrow cellularity of high dose l,3‐bis(2‐chloroethyl)‐l‐nitrosourea (BCNU) after HpD or dihematoporphyrin ether (DHE) pretreatment in C57BL/6J mice.The lethal toxicity of the LDS0+ 10% dose of BCNU (60 mg kg−1) was significantly reduced by pretreatment with HpD when the HpD was administered at least 3 days prior to the BCNU. HpD administered 1 or 2 days prior to BCNU or after BCNU had no effect. The percent death rate was reduced from 80 to 0% when HpD was administered 7 and 5 days prior to BCNU.No alteration of the lethal toxicity rate of BCNU at doses of 80 mg kg−1 were identified with DHE pretreatment although some increase in median survival was noted in two groups. Some reduction in lethal toxicity was noted when 60 mg kg−1 BCNU was used and the pretreatment dose of DHE was 10 or 25 mg kg−1 given twice 3 days apart. Furthermore, a significant reduction of BCNU induced marrow cell depletion was found when low doses of DHE were used as pretreatment. High doses of DHE resulted in marrow depletion. Both HpD and DHE altered the toxicity of BCNU.Should porphyrin photosensitizers, which alone have little toxicity, prove to protect against nitrosourea toxicity then an important dose limiting factor (myelotoxicity) could be altered if not reduction in the tumouricidal activity occurs.
A MORE EXACT THEORETICAL INTERPRETATION OF RECENT EXPERIMENTAL DATA OBTAINED USING THE SEPARATED SENSITIZER AND SUBSTRATE METHOD TO INVESTIGATE O2(lδg) INTERACTIONS. POSSIBLE IMPORTANCE OF O2(1σg+)
Authors: Parker J. G. 
Published: January 2008

Abstract— Recent experimental data obtained using the separated sensitizer and substrate method to investigate the interaction of O2(1δg) with various substances has been re‐interpreted by means of a more complete theory. Comparison of experimental and recalculated values of the dependence of relative reaction rates on the sensitizer‐substrate separation indicate general accord for experiments in which singlet oxygen acceptors in aqueous solution were used. The presumption is therefore that singlet molecular oxygen O2(1δg) is indeed the active oxidizing agent and that the theory presented and experiment are entirely in agreement.For experiments in which bacterial targets were used a very distinct disagreement between theory and experiment is evident, the conclusion being that the kill rate does not depend linearly on the O2(1δg) concentration in the immediate proximity of the bacteria. However, the data is consistent with a quadratic dependence on the 1δg concentration. A possible conclusion therefore is that the cytotoxic species is actually O2(1σ+g), formed by an energy pooling reaction involving two O2(1δg) molecules.
MODE OF COACTION BETWEEN UV‐A AND LIGHT ABSORBED BY PHYTOCHROME IN CONTROL OF APPEARANCE OF RIBULOSE‐1.5‐BISPHOSPHATE CARBOXYLASE IN THE SHOOT OF MILO (Sorghum vulgare Pers.)
Authors: Drumm‐Herrel Helga , Mohr Hans 
Published: January 2008

Abstract— In shoots of milo (Sorghum vulgare Pers.) appearance of ribulosebisphosphate carboxylase (RuBPCase) and of translatable mRNA for its small subunit is stimulated strongly by red light (R, operating through phytochrome) and UV‐A light (UV‐A). Ultraviolet‐A is more effective than R.The mode of coaction between phytochrome and light absorbed by the blue/UV‐A light photoreceptor (‘cryptochrome’) was analyzed in detail in case of enzyme appearance. Fluence rate dependencies, lagphases and the time course of the response are compatible with the view that UV‐A intensifies a process which is occurring in R alone albeit at a lower rate.With both light qualities the light effect is fully reversible by far‐red light up to 1 h. This means that during this period only phytochrome (Pfr) controls the terminal response, i.e. the actual appearance of RuBPCase. During this 1 h period after the onset of light UV‐A or R have no effect on the level of translatable mRNA for the small subunit of RuBPCase indicating that it requires more than 1 h for the light signal to affect gene expression.When R and UV‐A are given longer onset of escape from full reversibility is observed at the same time for both light qualities in the case of RuBPCase appearance. The extent of the reversible response is greater after UV‐A pretreatment than after a R pretreatment.It is argued that the data are consistent with the concept that phytochrome (Pfr) controls the terminal photoresponse, in the present case appearance of RuBPCase, while light absorbed via cryptochrome leads to an increase in responsiveness of the RuBPCase producing machinery towards Pfr.
MINIATURE PIG AS AN ANIMAL MODEL TO STUDY PHOTOAGING*
Authors: Fourtanier A. , Berrebi C. 
Published: January 2008

Abstract— Seven miniature pigs were irradiated thrice weekly over a 14 months period with suberythem‐atogenic doses of UVB and UVA. Another seven were not exposed, to record innate aging changes.Chronic irradiation induced the following changes: 1. Increased scaling, with thickening of the stratum corneum and decreased reactivity to acetic acid. 2. Increased minimum erythema dose, corresponding to decreased transmission of UV‐radiation through isolated epidermis. 3. Increased elastic fibers, accompanied by strong deposition of glycosaminoglycans in the upper dermis. 4. Increased laxity with greater extensibility to a deforming torque. 5. Increased density of vessels. 6. More disorderly arrangement of collagen bundles with minor alterations in collagen biochemistry.These changes mimic those in photoaged human skin but are milder in degree, attributable to the low total dosage of ultraviolet radiation.
RESISTANCE OF HUMAN and MOUSE MYELOID LEUKEMIA CELLS TO UV RADIATION
Authors: Poljak‐Blazi Marija , Osmak Maja , Hadzija M. 
Published: January 2008

Abstract—Sensitivity of mouse bone marrow and myeloid leukemia cells as well as the sensitivity of human myeloid leukemia cells to UV light was tested. Criteria were the in vivo colony‐forming ability of UV exposed cells and the inhibition of DNA synthesis during post‐irradiation incubation for 24 h in vitro. Mouse bone marrow cells irradiated with a small dose of UV light (5 J/m2) and injected into x‐irradiated animals did not form hemopoietic colonies on the recipients' spleens, and the recipients died. However, mouse leukemia cells, after irradiation with higher doses of UV light, retained the ability to form colonies on the spleens, and all recipient mice died with typical symptoms of leukemia. In vitro, mouse bone marrow cells exhibited high sensitivity to UV light as compared to mouse myeloid leukemia cells. Human leukemia cells were also resistant to UV light, but more sensitive than mouse leukemia cells. These results indicate that myeloid leukemia cells are resistant to UV light as compared with normal bone marrow cells.
DYNAMIC FLUORESCENCE OF TRYPTOPHANYL RESIDUES IN LOW MOLECULAR WEIGHT MODEL COMPOUNDS AND PROTEINS
Authors: Bismuto Ettore , Irace Gaetano 
Published: January 2008

Abstract—The tryptophanyl fluorescence decay of tuna apomyoglobin, a protein containing a single indole residue, has been compared to that of the monomeric tryptophanyl residue (NATA) in order to discriminate the effect determined by the protein matrix from those induced by physical and chemical agents. The fluorescence decay, obtained in the frequency domain, has been analyzed in terms of lifetime distributions having a Lorentzian shape. The results indicate that the incorporation of the chromophore into the protein matrix determines a broadening of the distribution pattern.A further increase of the distribution width has been observed on guanidine‐induced unfolding of the protein, whereas no effect has been detected for NATA in the presence of guanidine at concentrations as high as 6.0 M. These observations lead to the conclusion that the tryptophanyl fluorescence lifetime is influenced by the protein matrix even in the fully unfolded state.The increase of temperature from 20 to 45oC produces an enlargement of the distribution width of NATA and unfolded tuna apomyoglobin. In the same thermal range, the native protein exhibits a narrowing of the tryptophanyl lifetime distribution. This different behaviour has been explained in terms of a larger distribution of microenvironmental states, generated by the chromophore‐solvent interaction (which is very limited in the native protein), at higher temperature.This conclusion has been further corroborated by the observation that a temperature increase changes the weight of the various components which contribute to the total emission of the free amino acid tryptophan.
RELATIVE REPAIR OF ADENOVIRUS DAMAGED BY SUNLAMP, UV AND γ‐IRRADIATION IN COCKAYNE SYNDROME FIBROBLASTS IS DIFFERENT FROM THAT IN XERODERMA PIGMENTOSUM FIBROBLASTS
Authors: Rainbow Andrew J. 
Published: January 2008

Abstract—The DNA repair capacities of three unrelated Cockayne syndrome(CS) fibroblast strains were compared to that of three unrelated xeroderma pigmentosum(XP) strains for three different DNA damaging agents using a sensitive host cell reactivation(HCR) technique. Adenovirus type 2(Ad 2) was treated with either UV light, γ‐rays or sunlamp‐irradiation and subsequently assayed for its ability to form viral structural antigens(Vag) in the CS and XP strains using immunofluorescent straining. D37 values for the survival of Ad 2 Vag synthesis in the CS and XP strains, expressed as a percentage of those obtained in normal strains, were used as a measure of DNA repair capacity. Percent HCR values in the XP strains XP25RO, XP2BE and XP5BE respectively were lowest for UV(6, 14 and 6%), intermediate for sunlamp‐irradiation(18, 32 and 10%) and highest for 7‐irradiation(65, 61 and 60%), whereas for the CS strains CS1BE, CS3BE and CS278CTO respectively, percent HCR values were lowest for UV (26, 30 and 34%), intermediate for γ‐irradiation(61, 64 and 69%) and near normal for sunlamp‐irradiation(82, 73 and 89%). These results suggest that the spectrum of lesions' which is defectively repaired in CS is not the same as that which is defectively repaired in XP.
MEASUREMENT OF INDUCTION PERIODS IN INHIBITED FREE‐RADICAL OXIDATION BY INFRARED CHEMILUMINESCENCE AT 1270 nm
Authors: Lee S. H. , Niu Q. , Sheng X. C. , Mendenhall G. D. 
Published: January 2008

Abstract—Infrared chemiluminescence at 1.27 µ. appears after the consumption of phenolic inhibitors in solutions of 1‐tetralyl hydroperoxide in tert‐butylbenzene (BPh), initiated with di‐tert‐butyl hyponitrite (BHN) at 68oC. The induction periods with phenols were in excellent agreement with ones calculated from rates of decomposition of the initiator. Di‐(2,2,6,6‐tetramethyl‐4‐piperidinyl) sebacate, benzhyd‐rol, a derivative of benzhydrol, and di‐rerr‐butyl ketoxime under these conditions showed no inhibition or a weak effect. Initiated solutions 2.5 mM in p,p′‐di‐tert‐octyldiphenylamine showed no detectable emission at 1270 nm because of efficient quenching of 1O2 by diaryl nitroxides formed from the amine, and because the oxidation products of the amine are peroxy scavengers (Thomas, J. R. 1960, J. Amer. Chem. Soc. 82, 5955). The relative yields of IR luminescence from several alkyl hydroperoxides and oxygen‐hydrocarbon mixtures, initiated in each case by BHN, were found to vary substantially with the structure of the hydrocarbon and with the solvent.
A POSSIBLE CONTROL BY A PHYTOCHROME‐LIKE PHOTORECEPTOR OF CHLOROPHYLL SYNTHESIS IN THE GREEN ALGA Ulva rigida
Authors: Loapez‐Figueroa F. , Niell F. X. 
Published: January 2008

Abstract—Chlorophyll synthesis is stimulated by red light pulses in the green alga Ulva rigida C. Aghard. Chlorophyll synthesis in darkness is greater after longer red light pulses (30 min) than after shorter red light pulses (5 min). Chlorophyll synthesis was higher after red light pulses of 14 Wm‐2 fluence rate than after those of 7 Wm‐2. The effect of red light showed some far‐red reversibility. The reversion by far‐red light was higher after red light pulses of 4 min than after those of 30 min. These results indicate the existence of a rapid induction of chlorophyll synthesis during the red light pulses and a fast escape from photoreversibility. The percentage of reversion is also affected by the fluence rate of the light pulses. The reversion was reduced by about 15% when the photon fluence rate was increased from 7 to 14 Wm‐2. Reversion was also observed when red and far‐red light pulses were applied successively. Thus, phytochrome or a phytochrome‐like photoreceptor could be involved in the induction of chlorophyll synthesis in Ulva rigida.
PROBING THE STRUCTURE OF HPD BY FLUORESCENCE SPECTROSCOPY
Authors: Kessel David 
Published: January 2008

Abstract—Fluorescence emission spectra indicate that oligomers containing both hematoporphyrin and its dehydration products (vinyl porphyrins) comprise the tumor‐localizing fraction of HPD. In the relatively polar solvent methanol, the vinyl porphyrins exhibit reduced fluorescence yields while the hematoporphyrin residues are relatively resistant to fluorescence quenching by Fe+3. In the less polar solvent tetrahydrofuran, fluorescence from oligomeric vinyl porphyrins was enhanced, and Fe+3‐induced quenching of oligomeric hematoporphyrin promoted. These, together with other studies in biological systems, suggest a substantial degree of interaction among the porphyrin units contained in these oligomers, as a function of the polarity of the environment.
CONVEX CURVATURES OF ALKALINE ELUTION PROFILES OF DNA FROM HUMAN CELLS IRRADIATED WITH 405 nm UVA: EVIDENCE FOR INDUCTION OF SLOWLY DEVELOPING ALKALI‐LABILE SITES
Authors: Peak Meyrick J. , Peak Jennifer G. 
Published: January 2008

Abstract—The alkaline (pH 12.1) elution profiles of DNA from human P3 cells exposed to monochromatic 405 nm UVA radiation deviate from exponential: on a logarithmic plot of eluted fraction of DNA vs time of elution, the rate of elution accelerates for the first 6 h. Following this period, the profiles become exponential. In contrast, the elution profiles of DNA after 520 nm green light or ionizing radiation exposures (x‐ and gamma rays, and fission spectrum neutrons) are always strictly exponential, evidence that the convex profiles were not due to an artifact caused by elution technique. Holding the DNA at pH 12.1 for 6 h after 405‐nm exposures before initiating elution resulted in profiles that were close to exponential, with slopes similar to the final slopes observed following the 6‐h elution period in the original experiments. This is evidence that some DNA breaks develop slowly during the first 6 h of elution, as a result of exposure to alkali. Therefore, the DNA lesions induced by 405‐nm light as measured by the alkaline elution technique are apparently heterogeneous and include a major class of alkali‐labile sites that develop slowly during incubation at pH 12.1. Convex profiles also occur following exposure of the cells td visible light at 434 and 512 nm.
RAPID EQUILIBRATION OF OXYGEN IN FLUORESCENCE QUENCHING REACTIONS
Authors: Eftink Maurice R. , Ghiron Camillo A. 
Published: January 2008

Abstract—A simple means is described for the rapid equilibration of oxygen in fluorescence quenching reactions. This involves bubbling the gas through experimental solutions. With this procedure, data for Stern‐Volmer plots can be obtained in 1–2 h, without bubbling it takes approximately ten times as long to collect such data.
INCREASING INCIDENCE OF CUTANEOUS MELANOMA, ULTRAVIOLET RADIATION AND THE CLINICIAN
Authors: Cascinelu Natale , Marchesini Renato 
Published: January 2008

Abstract–Incidence of melanoma is certainly rising all over the world and this observation has been related to a more frequent and prolonged exposure to the rays of the sun.The authors critically review pertinent literature and conclude that descriptive epidemiology of melanoma does not give survival trends and does not support the claim that melanoma is ultraviolet (UV) dependent. Analytical epidemiology has not reached a consensus on this aspect.Experimental data available are also difficult to interpret because there are consistent differences of susceptibility to UV among different animals, among lamps used and methods of measuring employed in various laboratories.Information available shows that the maximal relative biological activity of UV in humans is at about 305 nm. This evaluation greatly depends on (1) thickness of the skin, (2) the quantity and quality of secretions that cover the skin, (3) cleaness of the skin, (4) the latitude, (5) the weather, (6) the hour of the day and (7) the presence of chemical carcinogens in the air and on the skin.The authors stress the importance of the criteria of clinical diagnosis recently introduced in clinical practice and higher public awareness as the causes of the increasing incidence of melanoma.
PHOTOCHEMISTRY OF POLYFUNCTIONAL MOLECULES. DEVELOPMENT OF ANTENNA CHROMOPHORES FOR SELF‐SENSITIZED PHOTOREDUCTION OF KETONES*
Authors: Wu Zheng‐Zhi , Morrison Harry 
Published: January 2008

Abstract–Model systems are reported which test the efficacy of potential aryl antenna groups designed to harvest photons and subsequently transfer electronic energy to a target ketone through singlet‐singlet energy transfer. The model series consists of 4‐aryl substituted cyclohexanones where the aryl groups are benzyloxy (5a), benzoyl (5b), and dimethylphenylsiloxy (5c). In each case, photolysis of isopropyl alcohol solutions of the substrate with 254 nm light results in photoreduction of the ketone to the corresponding alcohols, 6a‐6c. The most efficacious sensitizing antennae are the benzyloxy and dimethylphenylsiloxy chromophores, with quantum efficiencies for reduction equal to 0.57 and 0.48, respectively. Photophysical and photochemical studies on 5a confirm that energy transfer to the ketone is intramolecular with the rate constant for energy transfer estimated at 2.4 × 100 s‐1.