bluuebunny/crossref_metadata_2025_split huggingface dataset:
Derivatives of 5‐Aminolevulinic Acid for Photodynamic Therapy: Enzymatic Conversion into Protoporphyrin
Authors: Kloek Joris , Akkermans Willem , van Henegouwen Gerard M. J. Beijersbergen 
Published: January 2008

ABSTRACTIn recent years, 5‐aminolevulinic acid (ALA) has become a widespread agent for photodynamic therapy (PDT). In nucleated cells, ALA is converted into the endogenous photosensitizer protoporphyrin IX (PpIX). A major drawback of ALA is its low bioavailability. As a result, high doses of ALA must be administered in order to reach clinically relevant levels of PpIX. Moreover, only superficially located lesions can be treated as a result of the poor penetration of ALA into tissues. A possible solution for this problem may be provided by the prod rug concept. In the present study, prodrugs of ALA have been synthesized. These ALA prodrugs are shown to result in higher PpIX levels in cells than does ALA itself. Of a range of ester prodrugs of ALA, the ALA‐pentyl ester elicits the highest fluorescence. Further‐more, the enzymatic conversion of the derivatives into ALA and PpIX has been studied in lysed cells. Under these circumstances, the esters with the shorter alkyl chains induce the highest fluorescence. The alcohols that arise as side products from enzymatic conversion of the prodrugs are shown to have no influence on the experiments.
Mutagenesis Mediated by Triple Helix–Forming Oligonucleotides Conjugated to Psoralen: Effects of Linker Arm Length and Sequence Context
Authors: Raha Manidipa , Lacroix Laurent , Glazer Peter M. 
Published: January 2008

ABSTRACTTargeted mutagenesis and gene knock‐out can be mediated by triple helix‐forming oligonucleotides (TFO) linked to mutagenic agents, such as psoralen. However, this strategy is limited by the availability of homopurine/ homopyrimidine stretches at or near the target site because such sequences are required for high‐affinity triplex formation. To overcome this limitation, we have tested TFO conjugated to psoralen via linker arms of lengths varying from 2 to 86 bonds, thereby designed to deliver the psoralen at varying distances from the third strand binding site present at the 3’end of the supFG1 mutation reporter gene. Following triplex formation and UVA irradiation, mutations were detected using an SV40‐based shuttle vector assay in human cells. The frequency and distribution of mutations depended on the length of the linker arm. Precise targeting was observed only for linker arms of length 2 and 6, which also yielded the highest mutation frequencies (3 and 14%, respectively). Psoralen–TFO with longer tethers yielded mutations at multiple sites, with the maximum distance from the triplex site limited by the linker length but with the distribution within that range influenced by the propensity for psoralen intercalation at A:T base‐pair‐rich sites. Thus, gene modification can be extended beyond the site of third strand binding but with a decrease in the precision of the targeting.
Tryptophan Quenching of Zinc‐Phthalocyanine and Porphycene Fluorescence in Micellar CTAC
Authors: Daraio Marta E. , Völker Axel , Aramendia Pedro F. , Román Enrique San 
Published: January 2008

ABSTRACTSinglet excited state deactivation of a zinc phthalocyanine (ZnPc), porphycene (Po) and tetrapropyl‐porphycene (PrPo) by anionic tryptophan (Trp−) were investigated in cetyltrimethylammonium chloride (CTAC) micelles at pH 9.2 ± 0.1, regulated by a Tris buffer. Data obtained from steady‐state experiments over a wide range of detergent and added NaCl concentrations were analyzed by using a pseudophase ion‐exchange model (Abuin et al., J. Phys. Chem. 87, 5166–5172, 1983). The model was applied to derive singlet quenching rate constants for ZnPc and the porphycenes by Trp− and the selectivity coefficient for Trp/Cl exchange at the micellar surface. The results point to an electron transfer quenching. Neutral tryptophan also quenches efficiently ZnPc fluorescence in CTAC without added buffer and Trp− does not deactivate the triplet state of these dyes. By flash photolysis, only the absorption of the triplet species was detected.
UV Light‐induced Duplex‐to‐duplex Crosslinking of DNA Molecules in Aqueous Ethanol Solutions
Authors: PospíŠlová Šárka , Kypr Jaroslav 
Published: January 2008

ABSTRACTUltraviolet light is known to generate crosslinks between the complementary strands of DNA and between DNA and proteins. Here we demonstrate that the UV light also crosslinks DNA duplexes to other DNA duplexes. However, the duplex‐to‐duplex crosslinks only appear in the presence of about 75% (vol/vol) ethanol plus a millimolar or submillimolar concentration of monovalent or divalent cations, e.g. 2 mM Na+ Methanol or formamide are ineffective. The present observations provide a direct means to detect physical contacts of DNA molecules or their parts, e.g. during recombination. It is remarkable that the solution conditions leading to the duplex‐to‐duplex UV light‐induced crosslink formation are the same as those inducing the B‐to‐A conformational transition of DNA.
On the Apparent Lack of Oxygen Quenching of Triplet Excited States
Authors: White Emil H. , Roswell David F. 
Published: January 2008

ABSTRACTThe early observation that excited triplet states obtained chemically from trimethyldioxetane (and subsequent energy transfers) appeared not to be quenched by oxygen is now shown to be an artifact; acetaldehyde is a product of the reaction and via chemical reactions it scavenges oxygen present in the medium; the attendant extended lifetime of the triplet states then permits their employment in photochemical‐type reactions. The effect of the aldehyde can be over‐ridden through an efficient introduction of an excess of oxygen into the liquid reaction phase.
The Induction and Analysis of Micronuclei and Cell Killing by Ultraviolet‐B Radiation in Human Peripheral Blood Lymphocytes
Authors: Keulers Rob A. C. , de Roon Angelique R. , Roode Saskia de , Tates Ad D. 
Published: January 2008

ABSTRACTThe DNA‐damaging potential of ultraviolet‐B (UVB) radiation was investigated by analyzing the frequency and origin of micronuclei (MN) in cytokinesis‐blocked, binucleated (BN) peripheral blood lymphocytes (PBL) and cloning efficiencies (CE) of PBL after exposure to different fluences of UVB. In total, PBL obtained from five normal donors were investigated. The PBL from all donors showed a dose‐related, linear‐quadratic increase in the frequency of MN per 1000 BN cells and in the frequency of micronucleated BN cells. In two experiments the origin of UVB‐induced MN was studied by analyzing MN for the presence or absence of centromeres by applying the MN assay in combination with a centromeric probe and fluorescence in situ hybridization. This revealed, for the first time, that UVB‐induced MN were centromere negative, indicating that UVB acted exclusively as a clastogenic agent in the tested dose range. The PBL from all donors showed a clear dose‐dependent decrease in CE, after UVB exposure. The UVB‐exposed PBL from all donors showed an inverse relationship between the induction of MN and the decrease in CE, but regression analysis revealed no correlation between the induction of MN and the decrease in cell survival. It is concluded that UVB has a clastogenic and cytotoxic effect on PBL.
Photoactivated Psoralens Elicit Defense Genes and Phytoalexin Production in the Pea Plant
Authors: Parsons M. Angela , Hadwiger Lee A. 
Published: January 2008

ABSTRACTIn the pea plant (Pisum sativum), compounds that intercalate into DNA induce the production of ∼20 major proteins similar to the pattern induced during nonhost disease resistance to the bean fungal pathogen, Fusarium solani f.sp. phaseoli. The pea phytoalexin, pisatin, as well as RNA homologous to several disease‐resistance response (DRR) genes accumulate following treatment with these compounds. Psoralen was chosen to characterize this interaction further because it intercalates into DNA and, following irradiation with 365 nm UV light (UV365), forms covalent bonds with pyrimidines on either or both strands of DNA. This produces monoadducts or cross‐links, respectively. Dose experiments showed that 60 μg/mL 4′‐aminomethyl‐4,5′,8‐trimethylpsoralen followed by 18 J/cm2 UV365 was sufficient to produce an accumulation of pisatin similar to that produced in response to the fungus. Under these inducing conditions, there was an average of 0.19 adducts per kb of pea genomic DNA. The accumulation of pisatin and the RNA of several DRR genes by psoralen required photoactivation, which suggests that covalent binding to DNA was necessary for induction. As the promoters of several putative fungal‐induced pea genes contain long stretches of d(AT)n, which is the preferred psoralen photobinding site, restriction fragments spanning DRR genes were examined after in vivo psoralen treatment. The rate of crosslinking was compared between fungal‐induced and noninduced genes using a modified Southern blot analysis. Implications of the induction of the DRR due to psoralen binding are discussed.
Protection of UV‐induced Suppression of Skin Contact Hypersensitivity: A Common Feature of Flavonoids after Oral Administration?
Authors: Steerenberg P. A. , Garssen J. , Dortant P. , Hollman P. C. , Alink G. M. , Dekker M. , Bueno‐de‐Mesquita H. B. , Van Loveren H. 
Published: January 2008

ABSTRACTIn this study we investigated the effect of the dietary ingredients fruit and vegetable, green tea phenol extract (GTP) and the specific flavonoid components quercetin and chrysin on the UV‐induced suppression of the con‐tact hypersensitivity (CHS) response to picryl chloride (PCl). The SKH‐1 mice were fed with test diet from 2 or 4 weeks before and during the UV irradiation (daily, 95 mJ/cm2) and tested for the CHS ear‐swelling response 10 weeks after the onset of the irradiation. For the CHS, mice were immunized with PCl by epicutaneous application on nonirradiated sites. Four days after sensitization all mice were challenged on both sides of each ear by topical application of one drop PCl. In addition, from mice fed with the fruit and vegetable mixture the number of Langerhans cells (LC) were scored in the skin and from mice fed with quercetin, quercetin levels in plasma were measured at week 11 after the start of UV irradiation. It was found that fruit and vegetable (19% in the diet), GTP (0.1% and 0.01% in the drinking water), quercetin (1% in the diet) and chrysin (1% and 0.1% in the diet), prevented statistically significantly the UV‐induced suppression of CHS to PCl. In the skin of mice fed with fruit and vegetables combined with UV irradiation the number of LC were comparable to the control mice, whereas the number of LC were significantly diminished in mice treated with UV only. This protective effect on the presence of LC in the epidermis after UV irradiation, which was also observed in a previous study with quercetin, may play a role in the prevention of UV‐induced immunosuppression by the flavonoids tested. In conclusion, we found protection of flavonoids against UV‐induced effects on CHS, which may be a common feature of most flavonoids.
The Correct Use of “Average” Fluorescence Parameters
Authors: Sillen Alain , Engelborghs Yves 
Published: January 2008

ABSTRACTWhen more than one fluorophore is present or when one fluorophore displays a multiple exponential decay “average” fluorescence parameters are derived, which can be combined with “average” lifetimes for further interpretation. However, two kinds of average lifetimes are used in this context: the intensity and the amplitude average lifetime. In this paper the different average parameters are carefully analyzed and their “best” combinations are derived. These average parameters are analyzed in the context of external and internal dynamic and static quenching, Föster energy transfer and the calculation of the radiative rate constant. The use of the amplitude average lifetime for the analysis of multiple fluorophore‐containing systems and the detection of interactions is discussed.
Singlet Oxygen‐mediated Photobleaching of the Prosthetic Group in Hemoglobins and C‐Phycocyanin
Authors: Tapia Guillermina , Galetovic Alexandra , Lemp Else , Pino Eduardo , Lissi Eduardo 
Published: January 2008

AbstractProteins bearing colored prosthetic groups, such as the heme group in hemoglobin or the bilin group in c‐phy‐cocyanin, quench singlet oxygen by interactions at the apoprotein and the prosthetic group levels. In both proteins, chemical modification of the chromophore constitutes only a minor reaction pathway. While total deactivation of singlet oxygen takes place with rate constants of 4.0 times 109and 4.2 times 108M‐ls‐1for hemoglobin and phycocyanin, respectively, the bleaching of the chromophore takes place with rate constants of 3.2 times 106and ˜1 times 107M‐1s‐1. Irradiation of phycocyanin with red light bleaches the chromophore with low yields (˜0.8 times 10‐4). Part of this bleaching is mediated by singlet oxygen produced by the irradiation of the bilin group. The low relevance of the singlet oxygen pathway is compatible with a low quantum yield (˜10‐3) of free singlet oxygen production after irradiation of the protein.
A Model for the Interaction of 6‐Lauroyl‐2‐(N,N‐dimethylamino)naphthalene with Lipid Environments: Implications for Spectral Properties
Authors: Bagatoll Luis A. , Parasassi Tiziana , Fidelio Gerardo D. , Gratton Enrico 
Published: January 2008

AbstractAlthough 6‐lauroyl‐2‐(N,N‐dimethylamino)naphthalene (LAURDAN) is now widely used as a probe for lipid systems, most studies focus on the effect of the lipid environment on its emission properties but not on the excitation properties. The present study is intended to investigate the excitation properties of LAURDAN in diverse lipid environments. To this end, the fluorescence properties of LAURDAN were studied in synthetic ester and ether phosphatidylcholines and sphingomyelin vesicles below, at and above the corresponding lipid main phase‐transition temperature. The excitation spectra of LAURDAN in these environments always show at least two well‐resolved bands. In the different lipid vesicles the behavior of the red band in the LAURDAN excitation spectra is sensitive to the lipid chemical environment near the probe fluorescent moiety and to the packing of the different lipid phases (gel and liquid crystalline). We propose that the interaction between the LAURDAN di‐methylamino group and the ester linkage of ester phospholipids is responsible for the strong stabilization of LAURDAN's red excitation band in the gel phase of ester phospholipid vesicles. We discuss the consequence of these proposed ground‐state interactions on LAURDAN's emission generalized polarization function. In the context of variable excitation wavelengths, information concerning solvent dipolar relaxation through excitation generalized polarization function is also discussed.
UVA and UVB Radiation Differentially Regulate Vascular Endothelial Growth Factor Expression in Keratinocyte‐derived Cell Lines and in Human Keratinocytes
Authors: Mildner Michael , Weninger Wolfgang , Trautinger Franz , Ban Jozef , Tschachler Erwin 
Published: January 2008

AbstractVascular endothelial growth factor (VEGF) is a central regulator of neoangiogenesis in inflammatory and neoplastic conditions. Ultraviolet irradiation is one of the mainstays of dermatological therapy for various inflammatory skin diseases. In the present study we have compared the effects of UV irradiation on the production of VEGF by keratinocytes (KC) and by the KC‐derived cell lines A431 and HaCaT. Irradiation of A431 and HaCaT cells with both UVA (10 J/cm2and 20 J/cm2) and UVB (8 mj/cm2and 16 mj/cm2) led to strong upregulation of VEGF mRNA and protein. Induction of VEGF by UVA and UVB in these cells was mediated by different pathways, i.e. the generation of free radicals and the secretion of (a) soluble factor(s), respectively. Unlike KC‐derived cell lines, no increase in VEGF production was observed in KC in primary culture after irradiation with the same UV doses. Increasing the irradiation dose in these cells of UVA to 40 J/cm2led to a marked decrease in soluble VEGF, whereas doses as high as 32 mj/cm2UVB only minimally affected VEGF levels. Reduction of VEGF production by KC might contribute to the effect of UVA irradiation in inflammatory skin diseases. The differential response of primary KC and autonomously growing KC‐derived cell lines to the induction of VEGF by UV light could favor neoangiogenesis in the vicinity of epidermal tumor cells in vivo, thereby endowing them with a growth advantage over normal cells.
Subcellular Localization Patterns and Their Relationship to Photodynamic Activity of Pyropheophorbide‐a Derivatives
Authors: MacDonald Ian J. , Morgan Janet , Bellnier David A. , Paszkiewicz Geraldine ML , Whitaker James E. , Litchfield Debra J. , Dougherty Thomas J. 
Published: January 2008

AbstractTo determine if subcellular localization is important to photodynamic therapy (PDT) efficacy, an in vitro fluorescence microscopy study was conducted with a congeneric series of pyropheophorbide‐a derivatives in human pharyngeal squamous cell carcinoma (FaDu) cells and murine radiation‐induced fibrosarcoma (RIF) mutant cells. In the FaDu cells the octyl, decyl and dodecyl ether derivatives localized to the lysosomes at extracellular concentrations less than needed to produce a 50% cell kill (LD50). At extracellular concentrations equal or greater than the LD50 the compounds localized mainly to mitochondria. The propyl, pentyl, hexyl and heptyl ether derivatives localized mainly to the mitochondria at all concentrations studied. This suggested that mitochondria are a sensitive PDT target for these derivatives. Similar experiments were performed with two Photofrin®‐PDT resistant RIF cell lines, one of which was found to be resistant to hexyl ether derivative (C6) mediated‐PDT and the other sensitive to C6‐PDT relative to the parent line. At extracellular concentrations of C6 below the LD50 of each cell line, the mutants exhibited lysosomal localization. At concentrations above these values the patterns shifted to a mainly mitochondrial pattern. In these cell lines mitochondrial localization also correlated with PDT sensitivity. Localization to mitochondria or lysosomes appeared to be affected by the aggregation state of the congeners, all of which are highly aggregated in aqueous medium. Monomers apparently were the active fraction of these compounds because equalizing the extracellular monomer concentrations produced equivalent intracellular concentrations, photoxicity and localization patterns. Compounds that were mainly aggregates localized to the lysosomes where they were rendered less active. Mitochondria appear to be a sensitive target for pyro‐pheophorbide‐a‐mediated photodamage, and the degree of aggregation seems to be a determinant of the localization site.
AGE-RELATED SERIAL PLASMA CITRULLINE LEVELS IN PRETERM NEONATES
Authors: Ioannou Hariklia , Avgoustides-Savvopoulou Persephone , Diamanti Elisavet , Tsampoura Zoi , Drosou-Agakidou Vasiliki 
Published: January 2008

INTRODUCTION: Citrulline is a nonessential amino acid that is synthesized almost exclusively in the small intestine. In adults and children with short-bowel syndrome, citrulline has served as a reliable index of the remaining small intestine length. Citrulline is also a precursor of arginine, the role of which is crucial for neonatal metabolism and growth.
OBJECTIVE: We sought to determine serial plasma citrulline levels of preterm neonates to assess levels in accordance with age and intestinal maturation, which may serve as a baseline in the event of intestinal abnormalities such as necrotizing enterocolitis (a devastating complication in this age group).
METHODS: We measured serial plasma citrulline levels in 18 clinically stable neonates (gestational age: ≤32 weeks; birth weight: 1000–1750 g) on days 2, 7, 14, 21, and 28. Quantitative analysis of plasma citrulline levels was performed by ion-exchange chromatography with postcolumn derivatization.
RESULTS: In the study population, mean plasma citrulline levels showed a statistically significant increase from 19 ± 4 μmol/L on day 2 and 20 ± 4 μmol/L on day 7 to 23 ± 4 μmol/L on day 14, 29 ± 5 μmol/L on day 21, and 31 ± 5 μmol/L on day 28 (P &lt; .01). The route of feeding did not seem to have an affect on plasma levels of citrulline (similar values were obtained from neonates who were fed enterally and parenterally on day 7).
CONCLUSIONS: Citrulline levels in normal preterm neonates seem to be age-related and may serve as reference values, which facilitates the evaluation of compromised intestinal function in preterm neonates with severe gastrointestinal problems.
TOPICAL COCONUT OIL APPLICATION REDUCES TRANSEPIDERMAL WATER LOSS IN PRETERM VERY LOW BIRTH WEIGHT NEONATES: A RANDOMIZED CLINICAL TRIAL
Authors: Nangia Sushma , Paul Vinod , Chawla Deepak , Deorari Ashok 
Published: January 2008

INTRODUCTION: Topical emollients have been shown to reduce transepidermal water loss (TEWL). Such an effect of coconut oil (often used in traditional massage of infants in India) has not been studied.
OBJECTIVE: Our goal was to determine the efficacy of topical coconut-oil application in reducing TEWL in preterm very low birth weight (VLBW) neonates.
METHODS: Seventy-four preterm VLBW infants were randomly assigned at 12 hours of age to either 4 mL of topical coconut-oil application every 12 hours for 7 days (n = 37) or no oil application (n = 37). TEWL was measured at 12 hours of age and thereafter every 12 hours for 7 days in both groups by using a Vapometer (Delfin Technologies, Kuopio, Finland), a portable closed-chamber evaporimeter. The ambient and skin-surface relative humidity and temperature were recorded simultaneously.
RESULTS: Birth weight (1213 ± 214 vs 1164 ± 208 g), gestation (32 ± 2 vs 31 ± 2 weeks), and other baseline variables were comparable between the 2 groups. TEWL was significantly lower in the infants in the coconut-oil group at each point of measurement. Although TEWL declined for those in both groups during the first week of life, proportional reduction in TEWL in the infants in the coconut-oil group was much greater compared with controls. Significantly lower TEWL in the infants in the coconut-oil group persisted after adjusting for differences in baseline variables by using a generalized estimating equation population-averaged model (an advanced form of regression analysis) (mean difference: 6.8 g/m2 per hour all during first week of life [95% confidence interval: 3.5–10.2]; P = .000).
CONCLUSIONS: Coconut-oil application in preterm VLBW neonates reduced TEWL by as much as 46%. Such an impact is expected to be of clinical importance, because it could reduce initial weight loss, promote better growth, and reduce fluid requirements.