bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Transport Analysis of Daunorubicin by LoVo and LoVo/DX Cells
Authors: Andreoni A. , Colasanti A. , Colasanti P. , Kisslinger A. , Mastrocinque M. , Ricclo P. , Roberti G. 
Published: January 2008

AbstractWe describe a fluorometric technique for the measurement of transport parameters of fluorescent drugs through cellular membranes. Unlike other procedures, this method gives an accurate measure of drug accumulated in the cells and measures the fraction of free and bound drug in the cell. The kinetic parameters of transport through cellular membranes are determined using a simple three‐compartment model combined with fluorescence measurements performed on the extracellular medium and on Triton‐permeabilized cells during daunorubicin incorporation. With this technique we found that LoVo cells have a greater daunorubicin uptake, a similar input rate constant and a lower output rate constant than the drug‐resistant LoVo/DX cells.
A Method for Evaluation of UV and Biologically Effective Exposures to Plants
Authors: Parisi A. V. , Wong J. C. F. , Galea V. 
Published: January 2008

AbstractThis paper presents a method for evaluating the UV and biologically effective exposures to a plant canopy during the irradiation of soybean with supplemental levels of UV radiation in a greenhouse study. The method employs four materials as dosimeters that allow evaluation of the UV spectra. The exposures evaluated at three growth stages were less by factors of 0.44, 0.49 and 0.56 compared to the ambient exposures. At the end of the irradiation period, the ambient biologically effective exposure for generalized plant response was higher by 180% compared to that calculated over the canopy. This is the magnitude of the error in UV studies that provide the ambient exposure as a measure of the UV incident on the plant. Additionally, the difference between the ambient and canopy exposures varied during the growth stages. These results indicate that the dosimetric technique applied to evaluating the UV exposures over a plant canopy is a more accurate representation of the UV exposure incidence on a plant than any obtained by measuring the ambient exposures only.
Inactivation of Trypanosoma cruzi Trypomastigote Forms in Blood Components with a Psoralen and Ultraviolet A Light
Authors: Gottlieb Paul , Margolis‐Nunno Henrietta , Robinson Richard , Shen Li‐Gang , Chimezie Eleanor , Horowitz Bernard , Ben‐Hur Ehud 
Published: January 2008

ABSTRACTInactivation of the blood‐borne parasite Trypanosoma cruzi by UVA and 4′‐aminomethyl‐4,5′,8‐trimethylpsor‐alen (AMT) was studied in the blood components fresh frozen plasma (FFP) and platelet concentrate (PC). The AMT was utilized at a concentration of 50 μg/mL and the inactivation procedure included the flavonoid rutin (at 0.35 mM), a quencher of type I and type II photo‐reactants, which we have previously found to maintain platelet integrity during this treatment regimen. Within both FFP and PC, complete inactivation of the infective form of T. cruzi, the trypomastigote, was achieved at a UVA (320–400 nm radiation) fluence of 4.2 J/cm2. We note that while the infectivity of the parasite is eliminated at 4.2 J/cmZ the trypomastigote motility continues for at least 16 h post‐treatment and is inhibited only after much higher light doses. Isolation of total DNA from the parasite cells after treatment in the presence of 3H‐AMT indicated that at the lethal UVA fluence about 0.5 AMT adducts per kilobase pairs occurred. These results suggest that this psoralen plus UVA methodology, which shows promise in enhancing the viral safety of PC, may in addition eliminate bloodborne T. cruzi, the causative agent of Chagas disease.
Cysteine Derivatives Protect Against UV‐lnduced Reactive Intermediates in Human Keratinocytes: The Role of Glutathione Synthesis
Authors: Steenvoorden David P. T. , van Henegouwen Gerard M. J. Beijersbergen 
Published: January 2008

Abstract— Several recent studies have shown cysteine derivatives can protect against negative effects of UV exposure. In this study, an attempt was made to correlate cellular bioavailability and metabolism of cysteine derivatives with protection against UV‐induced reactive intermediates. Human keratinocytes were treated with cysteine, N‐ace‐tylcysteine(NAC), cysteine‐ethylester(CYSET) and N‐acetylcysteine‐ethylester. The uptake of the compounds and their metabolism to cysteine and eventually to glutathione(GSH) was measured. Large differences in uptake were observed, with CYSET resulting in the highest and NAC in the lowest intracellular thiol levels. The increase in intracellular GSH was similar for all derivatives with a maximum of 23‐54% over the control level. Protective efficacy of the derivatives was measured as the inhibition of binding of UV‐induced reactive intermediates from 8‐methoxypsoralen. There was only a small difference between the compounds, with maximum protection of 25‐31%. No relation was found between total intracellular thiol and protection. However, for NAC, there was a linear relation between GSH level and protective efficacy (r = 0.94). Even though this was not clear for the other derivatives(r = 0.55 for CYS; r= 0.60 for CYSET; r = 0.70 for NACET), it indicates that GSH synthesis is an important factor.This was confirmed by experiments using cells with irreversibly inhibited GSH synthesis. Even though the total intracellular thiol level was comparable to uninhibited cells, protection was decreased. We conclude that the intracellular GSH increase is the most important factor in photoprotection by cysteine derivatives.
Pulsed Photoacoustic Study of the Diffusion of Chromophores in Human Skin
Authors: Lahjomri F. , Puccetti G. , Leblanc R. M. , Alard V. , Denis A. , Trenchant J.‐F. 
Published: January 2008

AbstractThe technique of pulsed photoacoustic spectroscopy was used to investigate the diffusion of chromophores in human skin. The kinetic of diffusion has been studied for five solutions at different concentrations in a mixture of chromophores, as used in commercial sunscreens. In addition to the classical macroscopic interpretation of the diffusion process, a new method is shown to give more detailed information on chromophore presence at different depths in skin. For the first time, results are expressed in the frequency domain by means of the Fourier transform applied to the photoacoustic signal. The spectra are discussed versus the depth in skin samples and the time of diffusion kinetics. This new method of data analysis is shown to be very useful for understanding the influence of the internal structure of a medium on the penetration rate of chromophores into skin.
Synthesis and Photoreaction of a‐Methylene‐γ‐Butyrolactone‐Psoralen Heterodimers
Authors: Giménez‐Arnau Elena , Bussey Cécile , Lepoittevin Jean‐Pierre 
Published: January 2008

AbstractThree double‐headed molecules were synthesized by linking a photoreactive linear (1, 2) or angular (3) furocou‐marin via a linear 10‐ or 5‐carbon chain to an electro‐philic α‐methylene‐γ‐butyrolactone. The photochemical behavior of these molecules was investigated in ethanol at 365 nm and the photocycloadducts obtained from each compound were isolated and characterized. In all cases, the photoreactivity results showed the 3,4‐pyrone double bond of the psoralen (linear or angular) to be the most reactive and [2 + 2] intramolecular photocycloadducts between the 3,4‐pyrone and the exomethylenic double bonds were obtained. With compounds 1 and 2, two kinds of intramolecular photocycloadducts were obtained, namely cissyn‐exo derivatives in 46% and 36% yield, respectively, and trans‐syn‐exo derivatives in 14% and 18% yield, respectively. With compound 3, only the trans‐syn‐exo derivative was obtained in 33% yield.
Ultraviolet Irradiation Produces Novel Endonuclease Ill‐Sensitive Cytosine Photoproducts at Dipyrimidine Sites
Authors: Jen J. , Mitchell D. L. , Cunningham R. P. , Smith C. A. , Taylor J.‐S. , Cleaver J. E. 
Published: January 2008

AbstractUltraviolet light irradiation of DNA in vitro and in vivo induces cyclobutane dimers, (6–4) pyrimidine‐pyrimi‐done photoproducts and a variety of minor products. Using a denned DNA fragment, we have identified two classes of sites that can be cleaved by Escherichia coli endonuclease III: single cytokines whose heat lability corresponds to that of cytosine hydrates and more heat‐stable dipyrimidines containing cytosine. The dipyrimidine products are induced at sites suggestive of (6–4) photoproducts but are not recognized as (6–4) photoproducts by radioimmunoassay. Use of oligonucleotides containing a single cyclobutane thymine dimer, a (6–4) photoproduct or the Dewar photoisomer of the (6–4) photoproduct also indicated that these products are not substrates for endonuclease III. We have therefore identified a minor UV photoproduct that has the same sequence specificity as the two major dipyrimidine photoproducts; it may be a minor isomer, a unique derivative or an oxidative lesion confined to dipyrimidine sites. Its biological significance is not yet known but may be masked by the preponderance of major products at the same sites. Its occurrence at the particular site in dipyrimidine sequences involved in the mutagenic action of UV photoproducts suggests that it may play a role in generating C to T transitions that are common UV‐induced mutations.
Effects of Nonpolar and Polar Solvents on the Qx and QY Energies of Bacteriochlorophyll a and Bacteriopheophytin a
Authors: Limantara Leenawaty , Sakamoto Shun , Koyama Yasushi , Nagae Hiroyoshi 
Published: January 2008

AbstractThe effects of nonpolar and polar solvents on the Qx and Qy energies of bacteriochlorophyll (BChl) a and bacteriopheophytin (BPhe) a were examined by electronic absorption spectroscopy. All of the four different energies exhibited a linear dependence on R(n) = (n2 ‐ l)/(n2+ 2), where n is the refractive index of the solvent, in both nonpolar and polar solvents. The energy of each state of both pigments could be expressed as v = ‐dR(n) + e (in cm‐1) where coefficient d was related to the dispersive interaction between the solute and the solvent molecules. A theory developed by Nagae showed that coefficient d originates from the quantum‐mechanical fluctuation of the multipole moments of the solute, in terms of which the following characteristics of the observed d values were explained: (1) In all of the four cases of the Qx, and Qy energies of both BChl a and BPhe a, the d values for the polar solvents were smaller than those for the non‐polar solvents. (2) In both nonpolar and polar solvents, the d value of BChl a was larger than that of BPhe a in the Qy energy, whereas the d value of BPhe a was larger than that of BChl a in the Qx energy. (3) The d value of the Qx energy was larger than that of the Qy, energy for either case of BChl a or BPhe a.
Relationship between Skin Color and Sun Exposure History: A Statistical Classification Approach
Authors: Rubegni Pietro , Cevenini Gabriele , Flori Maria Laura , Fimiani Michele , Stanghellini Elisabetta , Molinu Antonietta , Barbini Paolo , Andreassi Lucio 
Published: January 2008

AbstractIn this study our aim was to determine the biophysical values of constitutive skin color in Caucasians and to define the correlation between skin color and phototype assessed according to the Fitzpatrick method. Constitutive skin color was measured on the buttock, with a Minolta CR‐200 colorimeter, in a population of 557 consecutive subjects belonging to phototype categories I, II, III and IV. The colorimeter expresses the results in five different color systems. We used the “Yxy” and L*a*b* systems, which are the most widespread in dermatology. Statistical analysis of the data showed that the “Yxy” system is even more discriminant than the L*a*b* system when the Fitzpatrick classification scheme is adopted as the reference and shows a poor ability to correctly classify the intermediate phototypes (II and III). On the contrary the “Yxy” system performs well in distinguishing phototypes I and IV. To establish whether this low discriminating capacity for phototypes II and III is related to a low discriminating capacity of the method suggested by Fitzpatrick or by our procedure, an objective technique (minimal erythemal dose) should be used to evaluate the percentage errors of classification of both the Fitzpatrick method and instrumental measurement of skin color. The results of such a study are extremely important because the evaluation of skin color is objective, simple and has potential applications in dermatology and cosmetology.
Characterization of DNA Damage Inflicted by Free Radicals from a Mutagenic Sunscreen Ingredient and Its Location Using an in vitro Genetic Reversion Assay
Authors: McHugh Peter J. , Knowland John 
Published: January 2008

AbstractWe describe an in vitro approach to assessing the potential genotoxicity of illuminated sunscreens. The photomutagenic sunscreen Padimate‐O attacks DNA on illumination with simulated sunlight, producing strand breaks and lesions that are labile to N, N'‐dimethylethy‐lenediamine but few, if any, cyclobutane dimers or other direct photoproducts. The damage can be completely suppressed by the free radical quenchers Tris, ethanol, mannitol and dimethylsulfoxide, which is commonly used as a solvent in conventional photomutagenicity assays. Using a genetic reversion assay that depends on regenerating P‐galactosidase activity in photodamaged plas‐mids we find that GC base pairs are particularly susceptible to attack by Padimate‐O.
Interaction of UV Light‐Induced α–Tocopherol Radicals with Lipids Detected by an Electron Spin Resonance Prooxidation Effect
Authors: Walke Mathias , Beckert Dieter , Lasch Jürgen 
Published: January 2008

AbstractThe reaction rate constants of the interaction between light‐induced α–tocopherol radicals with unsaturated lipids in a heterogeneous system compared to a homogeneous system are of the same order of magnitude. The decay rates of compartmentalized ‐α‐tocopherol radicals were significantly reduced by using negatively charged sodium dodecyl sulfate (SDS) micelles. A partially resolved electron spin resonance (ESR) hyperfine structure was observed under the conditions of both high lipid concentrations in comparison to the α‐tocopherol concentration and of a regular distribution of α‐tocopherol molecules inside the heterogeneous lipid structures. Alphα‐to‐copherol radicals have a considerable prooxidation potential at higher concentrations. Ascorbic acid dissolved in the aqueous medium provokes very fast ‐α‐tocopherol radical recycling through the boundary layer between the aqueous medium and micelles. By contrast, very slow reactions such as those of α‐tocopherol radicals with glutathione through this boundary layer are measurable. Despite using the heterogeneous SDS micellar system, the decay kinetics of the α‐tocopherol radical ESR signal is simply compounded. In addition to the known stabilization effect of cholesterol in membrane systems, cholesterol itself acts as a target molecule attacked by free radicals, e.g. ‐α‐tocopherol radicals. Using stratum corneum extracts that contain unsaturated lipids and cholesterol the ‐α‐tocopherol radical can prooxidatively react with these compounds. Using focused UV light generates a high radical yield in a relatively short time compared to the lifetime of the ‐α‐tocopherol radicals. The decay processes after radical induction can be characterized as consecutive reactions. The compartmentalization of radicals induced in SDS micelles and the close proximity of target molecules are essential if very slow one‐electron reductions are to be measured.
Photoprotection of Mammalian Acid‐Soluble Collagen by Cuttlefish Sepia Melanin In Vitro
Authors: Menter Julian M. , Patta Abrienne M. , Hollins Thomas D. , Moore Cyril L. , Willis Isaac 
Published: January 2008

AbstractSeveral important clinical conditions can result in close association between the pigment melanin and dermal collagen. Because melanin and its precursors can be chemically reactive in ground and excited states, it is important to know whether the resulting melanin‐collagen interaction results in photoprotection or photoaggression. Acidic and neutral air‐saturated collagen suspensions (0.033%) were irradiated with0–2.6 times 104 J/m2 UVC or with0–83 times 104 J/m2 solar‐simulating UV radiation (SSR). Photochemical destruction of a photolabile collagen fluorophore (δem 360 nm) and collagen chain degradation were monitored as functions of irradiation time in the presence and absence of added (0–100μg) sepia eumelanin. Melanin retarded collagen photodamage but did not qualitatively alter the fluorescence fading kinetics. Both H202 and 02 can be produced by UV irradiation of eumelanin. Added H202 and K02 destroyed collagen fluorescence and caused 50% chain degradation at ca10–20‐fold molar excess. Previous studies have demonstrated that eumelanins efficiently scavenge 02 . We demonstrated that eumelanin also efficiently scavenges H202 as evidenced by its ability to (a) compete with scopoletin for peroxide uptake and (b) directly take up H202 through a dialysis bag. The latter observation suggests that peroxide scavenging could occur in vivo by melanin sequestered in melanophages. Thus, neither UV‐generated 02 nor H202 are likely to be present in concentrations high enough to cause measurable collagen damage. Absorption and/or scattering of excitation radiation away from the target chromophore appears to be the primary photoprotection mechanism, although scavenging of active 02 intermediates may play an important, if subtle role.
A Comparison of the Photodynamic Effects of Temoporfin (mTHPC) and MC540 on Leukemia Cells: Efficacy and Apoptosis
Authors: Chen J. Y. , Mak N. K. , Wen J. M. , Leung W. N. , Chen S. C. , Fung M. C. , Cheung N. H. 
Published: January 2008

AbstractThe photodynamic effects of temoporfin (meso‐tetrahy‐droxyphenylchlorin, mTHPC) and merocyanine 540 (MC540) in murine myeloid leukemia M1 and WEHI 3B (JCS) cells were compared. The mTHPC was found to be more potent and selective. At a lethal dosage of 90% killing (LD90), only 1.3 μM of mTHPC and 4.2 kj/m2 of light irradiation was required, which was a 20‐fold lower drug concentration and 11‐fold smaller light dose than that required when using MC540. Meanwhile, three times less, or 15%, of the coincubated erythrocytes were destroyed by mTHPC than by MC540. Confocal micrographs showed that both drugs accumulated diffusely inside the cytoplasm in a very similar fashion, but mTHPC induced a more extensive apoptosis in photosensitized JCS cells. For example, at LD90, mTHPC practically killed all JCS cells via apoptosis and cleaved the DNA to extremely small 150 base‐pair fragments. In contrast, among the JCS cells killed by MC540, about 88% died via apoptosis and large DNA fragments were abundant. Relative to MC540, the ability of mTHPC to trigger large‐scale and thorough apoptosis in leukemia cells may help explain its potency and selectivity.
Transient Species in the Photochemistry of Tiaprofenic Acid and Its Decarboxylated Photoproduct*
Authors: Encinas Susana , Miranda Miguel A. , Marconi Giancarlo , Monti Sandra 
Published: January 2008

AbstractPhotoexcitation of tiaprofenic acid (TPA) in aqueous medium leads with almost unitary efficiency to the lowest π,π* triplet, which is detected by transient absorption. The deactivation of this state occurs in the microsecond time domain and is dominated by a thermally activated spin‐allowed process with –10 kcal/mol energy barrier. The occurrence of decarboxylation from an upper state, likely the second triplet of n, π* character, is confirmed by the study of the transients toward the final keto photoproduct, i.e. the benzoylthiophene ethyl derivative (DTPA). At neutral pH, upon adiabatic release of the CO2 fragment, long‐lived triplet biradicals and ground‐state intermediates with a protonated carbonyl oxygen are formed. Laser flash photolysis of DTPA leads almost quantitatively to the lowest π,π* triplet, with similar T‐T absorption features as those of TPA. However the DTPA triplet appears essentially unreactive in aqueous medium. In isopropanol H‐abstraction from the solvent is demonstrated by the formation of the ketyl radical.
Photobinding of Tiaprofenic Acid and Suprofen to Proteins and Cells: A Combined Study Using Radiolabeling, Antibodies and Laser Flash Photolysis of Model Bichromophores
Authors: Castell José V. , Hernández Daniel , Gómez‐Lechón María José , Lahoz Agustín , Miranda Miguel A. , Morera Isabel M. , Perez‐Prieto Julia , Sarabia Zaideth 
Published: January 2008

AbstractDrug photoallergy is a matter of current concern. It involves the formation of drug‐protein photoadducts (pho‐toantigens) that may ultimately trigger an immunological response. Tyrosine residues appear to be key binding sites in proteins. The present work has investigated the photobinding of tiaprofenic and (TPA) and the closely related isomer suprofen (SUP) to proteins and cells by means of radioactive labeling and drug‐directed antibodies. To ascertain whether preassociation with the protein may play a role in photoreactivity, two model bichro‐mophoric compounds (TPA‐Tyr and SUP‐Tyr) have been prepared and studied by laser flash photolysis. The results of this work show that (a) TPA and SUP photo‐bind to proteins with similar efficiencies, (b) both drugs form photoadducts that share a basic common structure, as they are recognized by the same antibody and (c) drug‐protein preassociation must play a key role in photoreactivity, as indicated by the dramatic decrease in the triplet state lifetimes of the model bichromophores compared to the parent drugs.
Molecular Requirement of Chlorosomal Chlorophylls. Self‐Organization of a Chlorophyll Derivative Possessing a Hydroxyl Group at Ring II
Authors: Oba Toru , Tamiaki Hitoshi 
Published: January 2008

ABSTRACTAggregation of zinc 71‐hydroxyl‐132‐demethoxycarbonyl‐pheophytin a (Zn‐71‐OH‐Chl) was examined in relation to the structure and function of the self‐aggregates of 31‐OH‐type chlorophylls (Chi) in chlorosomes of green photosynthetic bacteria. The Zn‐71‐OH‐Chl aggregates yielded a Qy absorption band at 712 nm with a 1.2‐fold larger width (full width at half maximum, 500 cm−1) than the monomer's (420 cm−1). Infrared and NMR spectroscopies revealed that each molecule in the aggregate links together with simultaneous coordination (C71‐OH…Zn) and hydrogen bonding (C71‐OH … O=C131). A nonlinear alignment of the constituent molecules in the oligomeric structure was assumed. Despite the similar molecular linkages, linearly aligned Qy, moments in the Zn‐31‐OH‐Chl aggregate gave a chlorosome‐like broader, more redshifted Qy band (740 nm; 670 cm−1, 2.1‐fold larger than the monomer's). Because it is advantageous for efficient light harvesting and energy transfer to have several Qy, spectral components, spread over a wide spectral range, that can act as the energy gradient, it is concluded that not only the intermolecular linkages but the linear locations of OH, C=0 and Mg in the molecule are crucial for photosynthetic antenna of the self‐assembled chiorosomal Chl.