bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of acid and alkali on the light absorption, energy transfer and secondary structures of core antenna subunits CP43 and CP47 of photosystem II
Authors: Shukui Guo , Chongqin Tang , Zhenle Yang , Liangbi Li , Tingyun Kuang , Yandao Gong , Nanming Zhao 
Published: July 2010

AbstractThe effects of acid and alkali treatment on the light absorption, energy transfer and protein secondary structure of the photosystem II core antenna CP43 and CP47 of spinach were investigated by the absorption spectra, fluorescence emission spectra and ciruclar dichroism spectra. It has been found that acid treatment caused the appearance of absorption characteristic of pheophytin a (Pheo a), whereas alkali treatment induced a new absorption peak at 642 nm. The energy transfer between β‐carotene and chlorophyll a (Chl a) in CP43 was easily disturbed by alkali, whereas in CP47 was readily affected by acid. As to the effects on the secondary structure of proetins in CP43 and CP47, effects of acid were far less than those of alkali. Both acid and alkali disturbed the microenvironment of Chl a and interfered exciton interaction between Chl a molecules. It was suggested that acid and alkali affect the light absorption, energy transfer and protein secondary structure of CP43 and CP47 in a differenty way. H+ can permeate into the internal space of α‐helix, change Chl a into Pheo a and disturb the microenvironment of pgiments without damaging the secondary structure of protein, whereas OH− can induce the protein unfolding at first, then saponify Chl a to chlorophyllide and disturb the microenvironment of pigments.
Angiogenesis Induced by Photodynamic Therapy in Normal Rat Brain¶
Authors: Jiang Feng , Zhang Zheng Gang , Katakowski Mark , Robin Adam M , Faber Michelle , Zhang Fan , Chopp Michael 
Published: July 2010

ABSTRACTAngiogenesis promotes tumor growth and invasiveness in brain. Because brain injury often induces expression of angiogenic‐promoting molecules, we hypothesize that oxidative insult induced by photodynamic therapy (PDT) could lead to an endogenous angiogenic response, possibly diminishing the efficacy of PDT treatment of tumors. Therefore, we sought to establish whether PDT induced an angiogenic response within the nontumored brain. PDT using Photofrin as a sensitizer at an optical dose of 140 J/cm2 was performed on normal rat brain (n = 30). Animals were sacrificed at 24 h, and 1,2,3 and 6 weeks after PDT treatment. Fluorescein isothiocyanatedextran perfusion was performed, and brains were fixed for immunohistological study. Immunostaining revealed that vascular endothelial growth factor (VEGF) expression increased within the PDT‐treated hemisphere 1 week after treatment and remained elevated for 6 weeks. Three‐dimensional morphologic analysis of vasculature within PDT‐treated and contralateral brain demonstrated PDT‐induced angiogenesis, as indicated by a significant increase in vessel connectivity (P < 0.001) concomitant with decreased (P < 0.05) mean segment length compared with vessels within the contralateral hemisphere. Volumetric measurement of angiogenic regions indicate that neovascular expansion continued for 4 weeks after PDT. These data demonstrate that PDT induces VEGF expression and neovascularization within normal brain. Because angiogenesis promotes growth and invasiveness of tumor, antagonizing this endogenous anglogenic response to PDT may present a practical means to enhance the efficacy of PDT.
Determination of the Minimal Erythema Dose and Colorimetric Measurements as Indicators of Skin Sensitivity to UV‐B Radiation¶
Authors: Dornelles Sérgio , Goldim José , Cestarl Tania 
Published: July 2010

ABSTRACTThere is a strong relation between chronic UV‐B‐induced sunburns and the development of skin cancer. Therefore, it is important to obtain a method that can be reproduced easily to detect individuals with similar skin color but different sensitiveness to sun exposure. The study evaluated 193 healthy volunteers (68% women; the average age was 38 years). They were divided into six groups of at least 30 subjects, according to skin type. The minimal erythema dose (MED) was assessed in two non‐sun‐exposed areas (thorax‐infra‐axillary area and on the buttocks), using a UV‐B source (0.5 mW/cm2), with openings of 1 cm2, in increasing doses. The same areas were evaluated with a Minolta CR 300 Chromameter (L*a*b* system). The MED values ranged from 13 to 156 mJ/cm2; the coordinate L* (brightness) ranged from 75.96 to 30.15. The correlation between the MED and the brightness was negative in both areas (Pearson's correlation r =−0.91, P < 0.05). Color measurements, especially brightness, can be used to quickly assess skin sensibility. Considering the MED, there is a substantial overlapping of adjacent phototypes, but they could be separated into two groups: more sensitive individuals (Types I, II, III and IV) and less sensitive ones (Types V and VI).
5‐Aminolevulinic Acid‐Based Photodynamic Therapy in Leukemia Cell HL60¶
Authors: Zhang Su‐Juan , Zhang Zhen‐Xi 
Published: July 2010

ABSTRACTA study to explore the optimal experimental parameters and the photosensitization of 5‐aminolevulinic acid (ALA)‐based photodynamic therapy (PDT) in promyelocytic leukemia cell HL60 has been conducted, in which HL60 cells and their control groups, peripheral blood mononuclear cell (PBMC), first are incubated with different concentrations of ALA in dark for different periods of time and then followed by irradiating with different wavebands for different fluences. Fluorescence microscope and spectrofluorometer have been used to detect the fluorescence of protoporphyrin IX (PpIX) endogenously produced by ALA. The response of the cells to ALA‐PDT was evaluated by the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2‐5‐diphenyl‐2H‐tetrazolium bromide (MTT) assay (interval between irradiation and the MTT assay is 24 h) and by flow cytometry (the length of time between irradiation and the flow assay is 30 min). MTT results will reflect the relative number of metabolically active mitochondria in the population. Propidium iodide uptake in flow cytometry will test for membrane damage. The results of parameter experiments were obtained: 1 × 105/mL HL60 cell was first incubated with 1 mmol/L ALA in dark for 4 h and the maximum fluorescence of PpIX level appeared; then irradiated with 410 nm (4 mW/cm2) for 14.4 J/cm2 and maximum photodamage to membrane and mitochondrial function of HL60 cell resulted. With the normal granulocytes, such response was not detected. Therefore a hypothetical idea can be brought forward that ALA‐based PDT can be used for inactivation of leukemia cell HL60 and these optimal parameters may be useful for clinical application.
Reduction in DNA Synthesis During Two‐photon Microscopy of Intrinsic Reduced Nicotinamide Adenine Dinucleotide Fluorescence¶
Authors: Nichols Michael G. , Barth Erin E. , Nichols Jennifer A. 
Published: July 2010

ABSTRACTTwo‐photon laser scanning microscopy (TPLSM) of endogenous reduced nicotinamide adenine dinucleotide (NAD(P)H) provides important information regarding the cellular metabolic state. When imaging the punctate mitochondrial fluorescence originating from NAD(P)H in a rat basophilic leukemia (RBL) cell at low laser powers, no morphological changes are evident, and photobleaching is not observed when many images are taken. At higher powers, mitochondrial NAD(P)H fluorescence bleaches rapidly. To assess the limitations of this technique and to quantify the extent of photodamage, we have measured the effect of TPLSM on DNA synthesis. Although previous reports have indicated a threshold power for “safe” two‐photon imaging, we find the laser power to be an insufficient indicator of photodamage. A more meaningful metric is a two‐photon‐absorbed dose that is proportional to the number of absorbed photon paris. A temporary reduction of DNA synthesis in RBL cells occurs whenever a threshold dose of approximately 2 × 1053 photon2 cm−4 s−1 is exceeded. This threshold is independent of laser intensity when imaging with average powers ranging from 5 to 17 mW at 740 nm. Beyond this threshold, the extent of the reduction is intensity dependent. DNA synthesis returns to control levels after a recovery period of several hours.
Self‐sensitized Photodegradation of Membrane‐bound Protoporphyrin Mediated by Chain Lipid Peroxidation: Inhibition by Nitric Oxide with Sustained Singlet Oxygen Damage
Authors: Niziolek Magdalena , Korytowski Witold , Girotti Albert W. 
Published: July 2010

ABSTRACTIn the presence of exciting light, iron and reductants, the singlet oxygen (1O2)‐generating sensitizer protoporphyrin IX (PpIX) induces free radical lipid peroxidation in membranes, but gradually degrades in the process. We postulated that NO, acting as a chain‐breaking antioxidant, would protect PpIX against degradation and consequently prolong its ability to produce1O2. This idea was tested by irradiating PpIX‐containing liposomes (LUVs) in the presence of iron and ascorbate, and monitoring the cholesterol hydroperoxides 5α‐OOH and 7α/β‐OOH as respective1O2and free radical reporters. 5α‐OOH accumulation, initially linear with light fluence, slowed progressively after prolonged irradiation, whereas 7α/β‐OOH accumulation only accelerated after an initial lag. The active, but not spent, NO donor spermine NONOate (0.4 mM) virtually abolished 7α/β‐OOH buildup as well as 5α‐OOH slowdown. Increasing membrane phospholipid unsaturation hastened the onset of rapid chain peroxidation and 5α‐OOH slowdown. Accompanying the 5α‐OOH effect was a steady decrease in1O2quantum yield and PpIX fluorescence at 632 nm, both of which were inhibited by NO. An NO‐inhibitable decay of PpIX fluorescence was also observed during dark incubation of 5α‐OOH‐bearing LUVs with iron and ascorbate, confirming a link between chain peroxidation and PpIX loss. By protecting PpIX in irradiated membranes, NO might select for and prolong purely1O2‐mediated damage. Supporting this was our observation that1O2‐mediated photoinactivation of a nonmembrane target, lactate dehydrogenase, slowed concurrently with 5α‐OOH accumulation and that spermine NONOate prevented this. Thus, NO not only protected membrane lipids against PpIX‐sensitized free radical damage, but PpIX itself, thereby extending its1O2‐generating lifetime. Consistent findings were obtained using porphyrin‐sensitized COH‐BR1 cells. These previously unrecognized effects of NO could have important bearing on 5‐aminolevulinate‐based photodynamic therapy in which PpIX is metabolically deposited in tumor cells.
Chemopreventive Action of Xanthone Derivatives on Photosensitized DNA Damage¶
Authors: Hirakawa Kazutaka , Yoshida Maim , Nagatsu Akito , Mizukami Hajime , Rana Virendra , Rawat Mohan Singh Maniyari , Oikawa Shinji , Kawanishi Shosuke 
Published: July 2010

ABSTRACTPhotosensitized DNA damage participates in solar‐UV carcinogenesis, photogenotoxicity and phototoxicity. A chemoprevention of photosensitized DNA damage is one of the most important methods for the above phototoxic effects. In this study, the chemopreventive action of xanthone (XAN) derivatives (bellidifolin [BEL], gentiacaulein [GEN], norswertianin [NOR] and swerchirin [SWE]) on DNA damage photosensitized by riboflavin was demonstrated using [32P]‐5′‐end‐labeled DNA fragments obtained from genes relevant to human cancer. GEN and NOR effectively inhibited the formation of piperidine‐labile products at consecutive G residues by photoexcited riboflavin, whereas BEL and SWE did not show significant inhibition of DNA damage. The four XAN derivatives decrease the formation of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐oxodGuo), an oxidative product of G, by photoexcited riboflavin. The preventive action for the 8‐oxodGuo formation of these XAN derivatives increased in the following order: GEN > NOR ≫ BEL > SWE. A fluorescence spectroscopic study and ab initio molecular orbital calculations suggested that the prevention of DNA photodamage is because of the quenching of the triplet excited state of riboflavin by XAN derivatives through electron transfer. This chemoprevention is based on neither antioxidation nor a physical sunscreen effect; rather, it is based on the quenching of a photosensitizer. In conclusion, XAN derivatives, especially GEN, may act as novel chemopreventive agents by the quenching mechanism of an excited photosensitizer.
Evaluation of a Single‐monochromator Diode Array Spectroradiometer for Sunbed UV‐radiation Measurements¶
Authors: Ylianttila Lasse , Visuri Reijo , Huurto Laura , Jokela Kari 
Published: July 2010

ABSTRACTThe suitability of a new technology single‐monochromator diode array spectroradiometer for UV‐radiation safety measurements, in particular for sunbed measurements, was evaluated. The linearity, cosine response, temperature response, wavelength scale, stray‐light and slit function of the spectroradiometer were determined and their effects on the measurement accuracy evaluated. The main error sources were stray‐light and nonideal cosine response, for which correction methods are presented. Without correction, the stray‐light may reduce the accuracy of the measurement excessively, particularly in the UV‐B range. The expanded uncertainty of the corrected UV measurements is estimated to be 14%, which is confirmed with the comparative measurements carried out with a well‐characterized double‐monochromator spectroradiometer. The measurement accuracy is sufficient for sunbed measurements, provided that all corrections described above have been done and the user of the instrument has a good understanding of the instrument's operating principles and potential error sources. If these requirements are met, the tested spectroradiometer improves and facilitates market surveillance field measurements of sunbeds.
The Photochemistry of Thymidylyl‐(3′‐5′)‐5‐methyl‐2′‐deoxycytidine in Aqueous Solution¶
Authors: Celewicz Lech , Mayer Moriz , Shetlar Martin D. 
Published: July 2010

ABSTRACTThe photochemistry of the dinucleoside monophosphate thymidylyl‐(3′‐5′)‐5‐methyl‐2′‐deoxycytidine (Tpm5dC) has been studied in aqueous solution using both 254 nm and UV‐B radiation. A variety of dinucleotide photoproducts containing 5‐methyl‐cytosine (m5C) have been isolated and characterized. These include two cyclobutane dimers (CBD) (thecis‐syn [c,s]andtranssynforms), a (6–4) adduct and its realted Dewar isomer, and two isomers of a product in which the m5C moiety was converted into an acrylamidine. Small amounts of thymidylyl‐(3′‐5′)‐thymidine (TpT) were also formed, presumably as a secondary photoreaction product. In addition, a photoproduct was characterized in which the m5C moiety was lost, thus generating 3′‐thymidylic acid esterified with 2′‐deoxyribose at the 5‐hydroxyl on the sugar mioety. Thec,sCBD of Tpm5dC readily undergoes deamination to form the corresponding CBD of TpT. The kinetics of this deamination process has been studied; the corresponding enthalpy and entropy of activation for the reaction have been evaluated at pH 7.4 as being, respectively, 73.4 kJ/mol and −103.5J/K mol. Deamination was not observed for the other characterized photoproducts of Tpm5dC.
UV Exposure of Elementary School Children in Five Japanese Cities¶
Authors: Ono Masaji , Munakata Nobuo , Watanabe Shaw 
Published: July 2010

ABSTRACTA 1 week UV‐exposure measurement and outdoor‐activity pattern survey was conducted for elementary school children for four seasons at five sites in Japan, i.e. Sapporo (43°05′N, altitude 40 m), Tsukuba (36°05′N, 20 m), Tokyo (35°40′N, 45 m), Miyazaki (31°60′N, 40 m) and Naha (26°10′N, 5 m), and UV exposure was measured directly and estimated using outdoor‐activity records. The study site with largest UV exposure was Miyazaki, a southern rural area. Comparing the results for boys and girls, UV exposure was larger in boys. UV exposure was large in spring and summer and small in winter. The total amount of UV exposure in spring and summer contributed 57.7–73.4% of total exposure for the year. As a whole, 8.1% and 1.8% of the schoolchildren were exposed to more than 1 minimum erythemal dose (MED) and 2 MED of solar UV in a day, respectively. The estimated yearly UV exposure ranged from 49 207 J/m2 in Miyazaki to 31 520 J/m2 in Tsukuba. The actual UV exposure correlated to potential UV exposure, estimated using outdoor‐activity records and ambient UV irradiance, but the ratio differed by season and site. The yearly average of percent UV exposure to ambient UV on a horizontal plane ranged from 9.9% in Tokyo to 4.0% in Naha. In the questionnaire survey on outdoor‐activity pattern, a short question “How long did you spend time outdoors between 0900 and 1500 h?” gives the best estimates of UV exposure.
Unexpected Photolysis of the Sunscreen Octinoxate in the Presence of the Sunscreen Avobenzone¶
Authors: Sayre Robert M. , Dowdy John C. , Gerwig Andre J. , Shlelds William J. , Lioyd Roger V. 
Published: July 2010

ABSTRACTA major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV‐A phototherapy lamp with additional UV‐B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high‐performance liquid chromatography techniques. The results show that UV‐induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended.
In Vivo Optical Analysis of Quantitative Changes in Collagen and Elastin During Arterial Remodeling¶
Authors: Christov Alexander , Korol Renee M. , Dai Erbin , Liu Liying , Guan Haiyan , Bernards Mark A. , Cavers Paul B. , Susko David , Lucas Alexandra 
Published: July 2010

ABSTRACTAltered collagen and elastin content correlates closely with remodeling of the arterial wall after injury. Optical analytical approaches have been shown to detect qualitative changes in plaque composition, but the capacity for detection of quantitative changes in arterial collagen and elastin content in vivo is not known. We have assessed fluorescence spectroscopy for detection of quantitative changes in arterial composition in situ, in rabbit models of angioplasty and stent implant. Fluorescence emission intensity (FEI) recorded at sites remote from the primary implant site was correlated with immunohistochemical (IH) analysis and extracted elastin and collagen. FEI was significantly decreased (P < 0.05) after treatment with anti‐inflammatory agents, and plaque area decreased on comparison with saline‐treated rabbits after stent implant or angioplasty (P≤ 0.013). Excellent correlations for FEI with elastin and collagen I, III and IV content measured by IH (R2≥ 0.961) analysis were detected by multiple regression (MR) analysis. Good correlations also were found for FEI with elastin and collagen measured by high‐performance liquid chromatography; MR analysis provided highly predictive values for collagen and elastin (R2≥ 0.994). Fluorescence spectroscopic analysis detects quantitative compositional changes in arterial connective tissue in vivo, demonstrating changes at sites remote from primary angioplasty and stent implant sites.
Photobiology of Ocular Melanocytes and Melanoma¶
Authors: Hu Dan‐Ning 
Published: July 2010

ABSTRACTThere are two different types of ocular melanocytes and melanomas. Conjunctival melanocytes are located on the surface of the eye and are exposed to visible light and UV radiation. Recently, epidemiological studies demonstrated that sunlight plays a definite role in the occurrence of conjunctival melanoma, as it does in cutaneous melanoma. Uveal melanocytes consist of the iridal melanocytes, which are exposed to visible light and UV radiation; and the ciliary body melanocytes and choroidal melanocytes, which are not exposed to light radiation. Epidemiological studies demonstrated that sunlight may play a role in the occurrence of iridal melanoma, but may not be a major factor in the etiology of ciliary body and choroidal melanomas. Uveal melanocytes differ from epidermal melanocytes in that epidermal melanocytes respond to UV radiation and skin color becomes darker after exposure to sunlight; but uveal melanocytes do not respond to UV radiation and the iris color remains stable after exposure to sunlight. Recently, in vitro studies indicate that this phenomenon is determined both by cellular factors and environmental factors.
Physical and Chemical Characterization of Iris and Choroid Melanosomes Isolated from Newborn and Mature Cows¶
Authors: Hong Lian , Simon John D. 
Published: July 2010

ABSTRACTBovine iris and choroid melanosomes at two ages (<1 week and >2 years) wer examined by inductively coupled plasma mass spectrometry (ICP‐MS), elemental analysis, infrared spectrometry (IR) and X‐ray photoelectron spectrometry (XPS). When iris and choroid melanosomes at the same age were compared, the quantification of metal elements by ICP‐MS revealed that choroid melanosomes had a higher binding capacity for the carboxylate‐binding metal ions (e.g. Na+, K+, Mg2+, Ca2+ and Zn2+). Elemental analysis showed a higher O:N ratio in choroid melanosomes. Both observations suggested that choroid melanosomes have a higher content of carboxylate‐containing monomer than iris melanosomes. IR spectrometric analysis showed a red shift (∼8 cm−1) ofthe absorption peak of aromatic C=C, C=N and C=O at ∼1630 cm−1 in the IR spectrum of iris melanosomes relative to choroid melanosomes. Increased conjugation in the molecular structure of the pigment is proposed to contribute to this peak shift. It is also notable that although the elemental anlaysis showed different C, N and O contents is the two types of melanosomes, XPS showed almost the same elemental compositions on the surface of two types of iris and choroid melanosomes studied. When the melanosomes from the same tissues at different ages were compared, ICP‐MS analysis suggested that the number of carboxylate groups in the melanosomes decreased with age. Both elemental analysis and XPS showed that C:N ratio decreased with age, which was proposed to be due to both a decrease in carboxylate groups in mature samples and to the fissure of phenol rings caused by age‐associated oxidation. Such age‐related oxidative damage diminishes conjugation and is manifested by blue shifts of absorption peaks for aromatic double bonds in the IR spectra of mature melanosomes. XPS analysis showed that the ratio of C‐O:C=O decreased with age. These tissue‐related and age‐related chemical differences between samples affected the optic density and metal binding properties of melanosomes, which are believed to be closely associated with the biological functions of melanins.