bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term Lens Organ Culture System with a Method for Monitoring Lens Optical Quality¶
Authors: Dovrat A. , Sivak J. G. 
Published: July 2010

ABSTRACTThe Scan Tox™ System is a method for monitoring lens optical quality (focus or lack of focus) in culture conditions, which mimic conditions inside the eye. The ocular lens is an ideal organ for long‐term culture experiments because it has no direct blood supply and no connection to the nervous system. The Scan Tox™ System makes it possible to keep lenses for long‐term studies of up to a few weeks. The use of cultured lenses, mainly bovine, replaces the need for testing the effects of potentially damaging agents on live animals. This optical monitoring apparatus uses a computer‐operated scanning laser beam, a video‐camera system and a video frame analyzer to record the focal length and transmittance of the cultured lens. The scanner is designed to measure the focal length at points across the diameter of the lens. The lens container permits the lens to be exposed to a vertical laser beam from below. The laser source projects its light onto a plain mirror, which is mounted at 45° on a carriage assembly. The mirror reflects the laser beam directly up through the test lens. The mirror carriage is connected to a positioning motor, which moves the laser beam across the lens. The camera sees the cross section of the beams and, by examining the image at each position of the mirror, Scan Tox™ software is able to measure the quality of the lens by calculating the back vertex distance for each beam position. The cultured lenses continue to maintain their original refractive function. When foreign substances are introduced to a cultured lens, the Scan Tox™ System measures the resulting optical response. This provides a very sensitive means to follow early damage to the eye lens. Because the lens is maintained in an intact state in solutions that are similar to those inside the eye, the lens retains its normal recuperative powers. So in addition to measuring early damage, this system allows measurement of recovery from damage.
Phototoxicity of Indocyanine Green on Human Retinal Pigment Epithelium in Vitro and its Reduction by Lutein¶
Authors: Wu Wen‐Chuan , Hu Dan‐Ning , Roberts Joan E. 
Published: July 2010

ABSTRACTPrevious work has shown that indocyanine green (ICG)‐assisted peeling of the internal limiting membrane during vitreoretinal surgery may damage the retinal pigment epithelium (RPE). The present study tested the direct toxic effects and phototoxic effects of ICG on cultured human RPE. RPE cells were exposed to ICG (0.5%, 5 min) with or without lutein (20 μM), followed by light irradiation at different doses of light energy (1.0,3.0 and 10.0 J/cm2). After 48 h, cells were collected and stained with trypan blue to obtain the number of viable and nonviable cells in different groups. Cultures exposed to ICG without light irradiation showed a significant decrease of viable cells (‐13.3%) and an increase of nonviable cells (x2.5‐fold) compared with cultures not exposed to either ICG or light, indicating the presence of direct toxic effects of ICG. In cultures exposed to ICG plus light irradiation (10.0 J/cm2), viable cells decreased significantly (‐45.0%) and nonviable cells increased significantly (x4.4‐fold) compared with cultures exposed to ICG alone. The damage to the RPE cells depended on the dose of light (1.0–10.0 J/cm2), indicating that ICG has a phototoxic effect as well as a toxic one. Lutein, an endogenous ocular antioxidant, had a protective effect on cultures exposed to ICG and light, cells treated with leutin showed an increase of viable cells (+74.6%) and decrease of nonviable cells (‐74.4%) compared with cultures without leutin but not on cultures exposed to ICG alone. Thus, it seems that photoactivated ICG kills cells through a photoxidative mechanism. Our study suggests that preoperative oral administration of lutein may protect against the phototoxic‐induced damage of ICG on the RPE cells.
Photochemical Behavior of 6‐Methylpterin in Aqueous Solutions: Generation of Reactive Oxygen Species¶
Authors: Cabrerizo Franco M. , Lorente Carolina , Vignonl Mariana , Cabrerizo Romina , Thomas Andrés H. , Capparelli Alberto L. 
Published: July 2010

ABSTRACTPterins are a family of heterocyclic compounds present in a wide range of living systems that participate in relevant biological functions and are involved in different photobiological processes. 6‐Methylpterin (MPT) was investigated for its efficiency of singlet‐oxygen (1O2) production and quenching in aqueous solution. The quantum yields of 1O2 production (φΔ) was determined by measurements of the 1O2 luminescence in the near‐infrared upon continuous excitation of the sensitizer. Values of φΔ were found to be 0.10 ± 0.02 and 0.14 ± 0.02 in acidic and alkaline media, respectively. Studies of the photo‐oxidation of MPT in acidic (pH = 5.0–6.0) and alkaline (pH = 10.2–10.8) aqueous solutions at 350 nm and room temperature have been performed. The photochemical reactions were followed by UV‐visible spectrophotometry, high‐performance liquid chromatography and an enzymatic method for H2O2 determination. MPT is not light sensitive in the absence of oxygen, but it undergoes a photooxidation reaction in the presence of oxygen, yielding several nonpteridinic products. The quantum yields of MPT disappearance were determined and values of 2.4 (±0.5) × 10−4 and 8.1 (±0.8) × 10−4 were obtained in acidic and alkaline media, respectively. H2O2 was detected and quantified in irradiated solutions of MPT. The rate constant of the chemical reaction between 1O2 and MPT (kr) was determined to be 4.9 × 106M−1 s−1 in alkaline medium and the role of 1O2 in the photooxidation of MPT is discussed.
Proteome Analysis of UV‐B‐Induced Anti‐apoptotic Regulatory Factors¶
Authors: Ibuki Yuko , Naitou Hirotaka , Ohashi Norio , Goto Rensuke 
Published: July 2010

ABSTRACTUltraviolet (UV) irradiation is well known to induce apoptosis, a hallmark event of which is the occurrence of sunburn cells in the epidermis. Keratinocytes in which DNA damaged by UV irradiation is not repaired undergo apoptosis as sunburn cells. However, we have previously reported that low‐dose UV‐B irradiation (∼0.1 J/cm2) suppressed the apoptosis induced by cell detachment and serum depletion. Dysregulation of apoptosis is important in tumor progression and malignancy and in promoting resistance to cancer therapy. To develop a better understanding of the antiapoptotic effect of UV irradiation, and to design the effective induction of apoptosis, we tried the proteome analysis of the molecules regulating apoptosis in low‐dose UV‐B‐irradiated NIH3T3 cells, using two‐dimensional difference gel electrophoresis (DIGE). Of a total of 3811 protein spots detected, 42 were found to be different between the cells undergoing apoptosis and cells after the irradiation. Of the spots selected, 25 were identified using MALDI‐TOF/TOF‐MS, some as structural proteins. Although typical apoptosis‐related molecules were not detected, possibly because proteins with low molecular weights were difficult to identify in the gel conditions used in this study, some of the proteins were considered to be involved in apoptosis. The DIGE system used in this experiment has advantages (including a high level of statistical confidence) for discovering new functional proteins related to the regulation of apoptosis.
Photophysical Parameters, Photosensitizer Retention and Tissue Optical Properties Completely Account for the Higher Photodynamic Efficacy of meso‐Tetra‐Hydroxyphenyl‐Chlorin vs Photofrin¶
Authors: Mitra Soumya , Foster Thomas H. 
Published: July 2010

ABSTRACTMeso‐tetra‐hydroxyphenyl‐chlorin (mTHPC) is one of the most potent photosensitizers currently available for clinical photodynamic therapy (PDT). However the reason or reasons for its high photodynamic efficacy remain(s) unresolved. To investigate the PDT efficacy of mTHPC vs Photofrin we use the knowledge of photophysical parameters extracted from the analysis of oxygen electrode measurements in spheroids to compute and compare their respective singlet oxygen (1O2 dose depositions. The electrode measurements indirectly report the bleaching kinetics of mTHPC and indicate that its photobleaching mechanism is consistent with 1O2‐mediated reactions. mTHPC's photodegradation via1O2 reactions is confirmed by a more direct evaluation of the spatially resolved fluorescence in confocal sections of intact spheroids during irradiation. The PDT efficacy comparisons establish that mTHPC's enhanced potency may be accounted for completely on the basis of its ability to sequester tightly in cells and its photophysical properties, in particular its higher extinction coefficient at a redshifted wavelength. We extend the efficacy comparison to include the influence of hemoglobin absorption of PDT treatment light and show that incorporating the influence of wavelength‐dependent light attenuation in tissue further contributes to significantly higher efficacy for mTHPC‐ vs Photofrin‐PDT.
Effect of Digitonin on the Rhodopsin Meta I‐Meta II Equilibrium¶
Authors: Szundi Istvan , Lewis James W. , Kliger David S. 
Published: July 2010

ABSTRACTAbsorbance difference spectra were recorded from 10 μs to 540 ms after photoexcitation of sonicated suspensions of hypotonically washed bovine rod outer segments with varying amounts of the detergent digitonin added (0 to 2%) at 20°C. Metarhodopsin I480 and metarhodopsin II displayed the expected anomalous pH dependence at pH 6 and 8 (i.e. opposite to that expected from direct protonation of the chromophore Schiff base). However, increasing levels of digitonin eliminated the pH dependence of the equilibrium, and at 2% digitonin the pH 6 and pH 8 data were both similar to the data collected at pH 8 without digitonin. Addition of 0.5% azolectin restored approximately 50% of the anomalous pH dependence at pH 6 in the 2% digitonin sample. The possibility that digitonin induced large‐scale aggregation of rhodopsin in the disk membrane that could be reversed by azolectin was tested using time‐resolved linear dichroism. Those results showed that even 0.3% digitonin disrupted the membrane, and no large aggregates were detectable under any conditions. Thus, digitonin reduces the activity of a component of the disk membrane required for metarhodopsin II formation, and that deficiency can be compensated for by azolectin.
Virus Particles and Receptor Interaction Monitored by Fluorescence Spectroscopy¶
Authors: Alimova Alexandra , Katz A. , Podder Rakhi , Minko Glenn , Wei Hui , Berriman John , Alfano R. R. , Gottlieb Paul 
Published: July 2010

ABSTRACTNative fluorescence spectroscopy (NFS), primarily from tryptophan (trp), was used for in situ investigation of the virus‐receptor attachment process in φ6, a lipid‐containing bacteriophage from the Cystoviridae family. NFS allowed us to monitor the viral attachment directly to its receptor, which was isolated from the pseudomonad host. Immediately upon mixing, an increase in tryptophan emission intensity was observed followed by a subsequent decrease in emission intensity. The initial increase in emission intensity reflects changes in trp quantum efficiency as the φ6 surface proteins change their conformation as a result of virus attachment to the pilus. The cystovirus spike protein P3 is responsible for receptor recognition and the fluorescence changes observed are likely to be the consequence of its conformational transition at this initial infection stage, providing a kinetic view of this process. The subsequent decrease in trp emission intensity could be due to changes in viral proteins as a result of disassembly of the pili. The technique may have important applications for the dynamic monitoring of additional stages of the virus replication cycle such as assembly, interaction with nucleic acids and maturation. This work expands on a previous demonstration that fluorescence offered a novel tool to detect virus particle interaction with its host cell.
Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials¶
Authors: Petrov E. P. , Clchos F. , Wagner F. , Spange St. , von Borczyskowski C. 
Published: July 2010

ABSTRACTDistibazolium dyes are investigated by steady‐state and time‐resolved fluorescence techniques in a series of low‐ and highviscosity polar solvents and in a silica sol‐gel matrix. In all solvents and the sol‐gel matrix, an interplay of photoinduced switching between different cis‐trans isomers and solvation dynamics is observed. Even in a viscous solution (glycerol) and in silica gel, cis‐trans isomerization is solvent‐controlled. Whereas in glycerol the solvation results in a time‐dependent fluorescence Stokes shift, the solvation‐induced spectral heterogeneity in silica gel is mostly static, possibly due to a close proximity of dye molecules to the silica surfaces of the nanopores. Compared to low‐viscosity solvents, where the cis‐trans isomerization process takes place with a solvent‐dependent rate on the timescale of about 120–150 ps, it slows down to about 1100–1400 ps in glycerol and about 1500 ps in a sol‐gel matrix. Additionally, fluorescence kinetics of the dyes in the sol‐gel reveals the presence of a range of different “frozen‐in” conformers exhibiting a broad spectrum of lifetimes from 20 to 300 ps.
Photophysical Properties of Methyl Triazone Included in MCM‐41¶
Authors: Ricci Andrea , Chrétien Michelle N. , Sayari Abdelhamid , Scaiano J. C. 
Published: July 2010

ABSTRACTMethyl triazone (4,4′,4″‐[l,3,5‐triazine‐2,4,6–triyItriimino]tris‐trimethyl benzoate) has been included in mesoporous MCM‐41 (Mobil's composition of matter‐41) silica, and its fluorescence emission has been compared in solution and in the solid state. Although inclusion does not affect significantly the absorption properties, a fluorescence emission shift and a behavior similar to the solid state has been observed by increasing the loading. It is believed that this observation reflects molecular aggregation inside the MCM‐41 channels. The potential of formulations of this type for sunscreen applications is discussed.
Protective Effects of an Antioxidant Derived from Serine and Vitamin B6 on Skin Photoaging in Hairless Mice¶
Authors: Kitazawa Manabu , Ishitsuka Yukiko , Kobayashi Misako , Nakano Takashi , Iwasaki Keiji , Sakamoto Kazutami , Arakane Kumi , Suzuki Tadashi , Kligman Lorralne H. 
Published: July 2010

ABSTRACTThe generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N‐(4‐pyridoxylmethylene)‐L‐serine (PYSer) was designed as an antioxidant to suppress iron‐catalyzed ROS generation by its iron‐sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV‐B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV‐B irradiation. A histological study indicated that UV‐B‐induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV‐B‐induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron‐sequestering activity.
Monitoring Cell Survival After Extraction of a Single Subcellular Organelle Using Optical Trapping and Pulsed‐Nitrogen Laser Ablation¶
Authors: Shelby J. Patrick , Edgar J. Scott , Chiu Daniel T. 
Published: July 2010

ABSTRACTThis paper characterizes cell viability in three different cell lines—Chinese hamster ovary cells (CHO), neuroblastoma cells fused with glialoma cells (NG108‐15) and murine embryonic stem cells (ES‐D3)—after N2 laser disruption of the cell membrane and removal, via optical trapping, of a single subcellular organelle. Morphological changes and viability (as determined by live/dead fluorescent stains) of the cell were monitored every half hour over a 4‐h period postsurgery. The ability of the cell to survive organelle extraction was found to depend both on the conditions under which surgery was performed and on the cell type. The average viability after surgery for CHO cells was approximately 80%, for NG 108 cells it was approximately 30% and for ES‐D3 cells postsurgery viability was approximately 10%. From over 600 surgeries we found the survival of the cell is determined almost exclusively within the first hour postsurgery regardless of cell line. The optimal pulse energy for N2 laser ablation was approximately 0.7 μJ. The N2 pulse produced an approximately 1–3 μm hole in the cell membrane and proved to be the primary source of cell death in those cells that did not survive the procedure.
UV‐A Fingerprint Mutations in Human Skin Cancer¶
Authors: Halliday Gary M. , Agar Nita S. , Barnetson Ross St.C. , Ananthaswamy Honnavara N. , Jones Alexandra M. 
Published: July 2010

ABSTRACTThis review of our work, presented at the Photocarcinogenesis Symposium of the 14th International Congress on Photobiology, shows that UV‐A causes a similar number of gene mutations as UV‐B in human skin cancer. Areas of about 20 keratinocytes from solar keratoses and squamous cell carcinomas, which are benign and malignant skin cancers, respectively, were sampled by laser capture microdissection. Automated sequencing of the p53 gene was used to detect mutations in these tumor areas, and the cause of the mutations was attributed on the basis of previously published studies. UV‐A and UV‐B caused similar numbers of p53 gene mutations in both benign and malignant human skin tumors, with UV‐B–induced mutations being restricted to the upper areas of the tumors and UV‐A–induced mutations predominating at the basal layer. Furthermore, each microdissected region within a tumor had distinct mutations showing that the skin tumors consisted of different clones of cells. This is not consistent with how human skin carcinogenesis is currently understood, and hypotheses to explain our data are presented. We propose that the UV‐A waveband of sunlight is as important as UV‐B in causing skin cancer in humans.
Inverse Relationship Between Increased Apoptosis and Decreased Skin Cancer in UV‐irradiated CD1d‐/‐ Mice¶
Authors: Matsumura Yasuhiro , Moodycliffe Angus M. , Nghiem Dat X. , Ullrich Stephen E. , Ananthaswamy Honnavara N. 
Published: July 2010

ABSTRACTWe previously demonstrated that CD1d knockout mice were resistant to ultraviolet (UV)‐induced immunosuppression. Because immune suppression is a critical factor in the development of UV‐induced skin cancers, we investigated the response of wild type (WT) and CD1d‐/‐ mice to UV carcinogenesis. We found that although 100% of WT mice developed skin tumors after 45 weeks of UV irradiation, only 60% of CD1d‐/‐ mice developed skin tumors. To investigate the mechanisms involved in the resistance of CD1d‐/‐ mice to UV‐induced carcinogenesis, we determined the time course and kinetics of keratinocyte cell death after UV irradiation. After acute UV exposure, the terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end‐labeling (TUNEL)‐positive keratinocytes were eliminated from the skin of WT mice by 72 h post‐UV, but they still persisted until 96 h in CD1d‐/‐ mice. The kinetics of p53 protein expression closely followed the kinetics of apoptotic cell death. Chronic UV irradiation resulted in induction of a significantly higher number of apoptotic keratinocytes in CD1d‐/‐ than WT mice. In addition, epidermis and dermis from chronically UV‐irradiated CD1d‐/‐ mice harbored significantly fewer p53 mutations than WT mice. These results indicate that the resistance of CD1d‐/‐ mice to UV carcinogenesis may be due to increased cell death and elimination of keratinocytes and fibroblasts containing DNA damage and p53 mutations.
UV Exposure, Genetic Targets in Melanocytic Tumors and Transgenic Mouse Models¶
Authors: de Gruijl Frank R. , Van Kranen Henk J. , Van Schanke Arne 
Published: July 2010

ABSTRACTThe genetic changes and corruption of kinase activity in melanomas appear to revolve around a central axis: mitogenic signaling along the RAS pathway down to transcription regulation by pRB. Epidemiological studies point to the importance of ultraviolet (UV) radiation in the etiology of melanoma, but where and how UV radiation is targeted to contribute to the oncogenic signaling remains obscure. Animal models of melanoma genesis could serve to clarify this issue, but many of these models are not responsive to UV exposure. Most interesting advances have been made by using transgenic mice that carry genetic defects that are known to be relevant to human melanoma: specifically, dysfunction in the tumor suppressive action of p161NK4a or a receptor tyrosine kinase/RAS pathway, that is constitutively activated in melanocytes. The latter types of mice appear to be most responsive to (neonatal) UV exposure. Whether this is due to a general increase in target cells by melanocytosis and a paucity or complete lack of pigment, or a possible UV‐induced response of the promoter–enhancer of the transgene or a genuinely independent and additional genetic alteration caused by UV exposure needs to be established. Importantly, the full effect of UV radiation needs to be ascertained in mice with different pigmentation by varying the wavelengths, UV‐B versus UV‐A1, and the exposure schedules, i.e. neonatal versus adult and chronic versus intermittent overexposure. Intermittent UV‐B overexposure deserves special attention because it most strongly evokes proliferative responses in melanocytes.
DNA Molecular Photonics¶†
Authors: Lewis Frederick D. 
Published: July 2010

ABSTRACTSynthetic DNA conjugates in which one or both ends of a short duplex is capped by a stilbene chromophore have been prepared and characterized crystallographically. Selective excitation of the chromophore can be used to initiate electron transfer processes in which a nucleobase serves as either an electron donor or an electron acceptor. These processes include hole‐ and electron injection and hole migration. The dynamics of these processes and its dependence on distance, driving force, and base sequence have been investigated by means of femtosecond time‐resolved spectroscopy. Duplexes with identical chromophores at both ends have been used to study both the dynamics of electron transfer processes and exciton coupling between the two chromophores by means of circular dichroism spectroscopy. Duplexes with different chromophores can also be used to study distance dependence of both electron transfer and exciton coupling.