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Tendências mais recentes na fotoproteção

Noronha, Mariana David Miranda de 
Fonte: Repositório Científico Lusófona Publicador: Repositório Científico Lusófona
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
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A exposição à radiação ultravioleta (UV) está associada a uma variedade de efeitos negativos causados no organismo humano. Este espectro de radiação UV divide-se em UVA (320-400nm), responsável pelo aparecimento dos sinais do envelhecimento cutâneo e danos indiretos no DNA, em UVB (290-320nm), responsável pelo eritema solar e danos diretos no DNA, e em UVC (100-290nm), cuja radiação fica retida na camada de ozono. A pele apresenta um mecanismo de defesa natural contra a radiação UV, mas este confere uma proteção limitada, tornando-se indispensável o recurso à fotoproteção. A utilização de vestuário adequado, chapéu e óculos de sol durante a exposição solar têm sido reconhecidas como medidas importantes de fotoproteção, em complementaridade com um protetor solar. Os filtros dos protetores solares são selecionados e aprovados por agências reguladoras da região em que o produto é comercializado. Na União Europeia existem atualmente 28 filtros para radiação UV aprovados. Esta dissertação aborda as últimas tendências na área da fotoproteção. Os últimos desenvolvimentos na área dos protetores solares sugerem filtros solares que compreendam ação sobre a radiação UVA e UVB e IV, em associação com outros compostos que demonstram propriedades reparadoras a nível tópico...

Proteção à radiação ultravioleta: recursos disponíveis na atualidade em fotoproteção; Ultraviolet radiation protection: current available resources in photoprotection

BALOGH, Tatiana Santana; VELASCO, Maria Valéria Robles; PEDRIALI, Carla Aparecida; KANEKO, Telma Mary; BABY, André Rolim
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica
Português
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A radiação ultravioleta pode provocar danos ao DNA, imunossupressão, alterações químicas e histológicas na epiderme, envelhecimento precoce, cataratas e carcinogênese, dentre outras deteriorações. A fotoproteção previne estes e outros efeitos danosos da radiação ultravioleta. Protetores solares, vestimentas, acessórios adequados e exposição segura ao sol são ferramentas essenciais da fotoproteção. Neste artigo, são apresentadas e discutidas as principais formas de fotoproteção, incluindo os protetores solares com filtros inorgânicos e orgânicos, a avaliação da eficácia dos mesmos e atualizações envolvendo o tema; Ultraviolet radiation can damage the DNA, cause immunosuppression, chemical and histological alterations in the epidermis, early photoaging, cataracts and carcinogenesis, among others. Photoprotection prevents these and other harmful effects of ultraviolet radiation. Sunscreens, protective clothing, proper accessories and safe sun exposure are essential photoprotection tools. The main forms of photoprotection are presented and discussed in this article, including sunscreens containing organic and inorganic filters, the assessment of their efficacy and current developments on the topic

Broad spectrum bioactive sunscreens

VELASCO, Maria Valerie Robles; SARRUF, Fernanda Daud; SALGADO-SANTOS, Idalina Maria Nunes; HAROUTIOUNIAN-FILHO, Carlos Alberto; KANEKO, Telma Mary; BABY, Andre Rolim
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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The development of sunscreens containing reduced concentration of chemical UV filters, even though, possessing broad spectrum effectiveness with the use of natural raw materials that improve and infer UV absorption is of great interest. Due to the structural similarities between polyphenolic compounds and organic UV filters, they might exert photoprotection activity. The objective of the present research work was to develop bioactive sunscreen delivery systems containing rutin, Passiflora incarnata L. and Plantago lanceolata extracts associated or not with organic and inorganic UV filters. UV transmission of the sunscreen delivery system films was performed by using diffuse transmittance measurements coupling to an integrating sphere. In vitro photoprotection efficacy was evaluated according to the following parameters: estimated sun protection factor (SPF); Boot`s Star Rating category; UVA/UVB ratio; and critical wavelength (lambda(c)). Sunscreen delivery systems obtained SPF values ranging from 0.972 +/- 0.004 to 28.064 +/- 2.429 and bioactive compounds interacted with the UV filters positive and negatively. This behavior may be attributed to: the composition of the delivery system: the presence of inorganic UV filter and quantitative composition of the organic UV filters; and the phytochemical composition of the P. incarnate L and P. lanceolato extracts. Among all associations of bioactive compounds and UV filters...

DNA Dosimetry Assessment for Sunscreen Genotoxic Photoprotection

Schuch, André Passaglia; Lago, Juliana Carvalhaes; Yagura, Teiti; Menck, Carlos Frederico Martins
Fonte: PUBLIC LIBRARY SCIENCE; SAN FRANCISCO Publicador: PUBLIC LIBRARY SCIENCE; SAN FRANCISCO
Tipo: Artigo de Revista Científica
Português
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Background: Due to the increase of solar ultraviolet radiation (UV) incidence over the last few decades, the use of sunscreen has been widely adopted for skin protection. However, considering the high efficiency of sunlight-induced DNA lesions, it is critical to improve upon the current approaches that are used to evaluate protection factors. An alternative approach to evaluate the photoprotection provided by sunscreens against daily UV radiation-induced DNA damage is provided by the systematic use of a DNA dosimeter. Methodology/Principal Findings: The Sun Protection Factor for DNA (DNA-SPF) is calculated by using specific DNA repair enzymes, and it is defined as the capacity for inhibiting the generation of cyclobutane pyrimidine dimers (CPD) and oxidised DNA bases compared with unprotected control samples. Five different commercial brands of sunscreen were initially evaluated, and further studies extended the analysis to include 17 other products representing various formulations and Sun Protection Factors (SPF). Overall, all of the commercial brands of SPF 30 sunscreens provided sufficient protection against simulated sunlight genotoxicity. In addition, this DNA biosensor was useful for rapidly screening the biological protection properties of the various sunscreen formulations. Conclusions/Significance: The application of the DNA dosimeter is demonstrated as an alternative...

Fotoproteção em Gracilaria tenuistipitata (Rhodophyta): uma abordagem fisiológica e molecular; Photoprotection of Gracilaria tenuistipitata (Rhodophyta): a physiological and molecular approach

Barufi, José Bonomi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/03/2010 Português
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A alga vermelha Gracilaria tenuistipitata tem sido utilizada como matéria prima para a produção de ágar e também como modelo para estudos fisiológicos e moleculares. Este trabalho analisou estratégias de fotoproteção contra a radiação UV dessa macroalga por meio de abordagens fisiológicas e moleculares, considerando a previsão de incremento de radiação UVB nas zonas tropicais do planeta nos próximos anos. Além disso, a interação entre a radiação UV e o suprimento de N foi também investigada. Essa interação estimulou a síntese de aminoácidos tipo micosporinas (MAAs) e outros compostos nitrogenados, o que proporciona proteção contra danos no aparato fotossintetizante. O envolvimento de um fotorreceptor para radiação UVA que regule a síntese de MAAs, com o efeito adicional de um segundo fotorreceptor, para radiação UVB é sugerido. Houve uma dependência da dose de radiação UV para aumento de MAAs. O aumento da intensidade da radiação UV causou efeitos negativos nos parâmetros da fotossíntese. Outra abordagem mostrou que a ausência de UVA causou danos ao DNA, com a presença de dímeros de ciclobutano pirimidina após 48 h de exposição à radiação PAR+UVB. Este estudo alerta para a importância da qualidade da radiação de UV e seu efeito biológico efetivo para danos no DNA e na fotoinibição. Fotoliases podem ter sido ativadas para evitar danos no DNA sob tratamentos com a presença de radiação UVA...

Desenvolvimento, avaliação da eficácia e estabilidade de formulações fotoprotetoras bioativas; Development, evaluation of the effectiveness and stability of bioactive sunscreens

Nishikawa, Deborah de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/09/2012 Português
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A exposição ao sol traz benefícios à saúde, no entanto, o excesso pode ocasionar danos cutâneos agudos e crônicos, dentre os quais se destacam as neoplasias. A fotoproteção é um método para a prevenção dos efeitos danosos da radiação ultravioleta (UV) e a biodiversidade Brasileira é campo fértil para as pesquisas nesta área. Dessa forma, os objetivos da presente pesquisa envolveram o desenvolvimento de formulações fotoprotetoras bioativas contendo rutina ou quercetina (compostos bioativos) e filtros solares físicos (dióxido de titânio e óxido de zinco); a caracterização das formulações por meio de ensaios físico (viscosidade aparente) e físico-químico (valor de pH); a determinação da eficácia fotoprotetora estimada por espectrofotometria de refletância difusa com esfera de integração; e a avaliação da estabilidade das preparações por meio do Teste de Estabilidade Normal (TEN). Na etapa do Desenvolvimento, a preparação composta por Dermabase® vegetal (10,0% p/p); sistema umectante (8,0% p/p); sistema emoliente (6,0% p/p); sistema quelante/antioxidante (0,6% p/p); sistema conservante (1,0% p/p); e água destilada recém destilada (74,4% p/p), foi selecionada como a formulação-base. As preparações contendo os compostos bioativos e ativos...

Uso cosmético de extratos glicólicos: avaliação da atividade antioxidante, estudo da estabilidade e potencial fotoprotetor; Cosmetic use of glycolic extracts: antioxidant activity evaluation, stability study and photoprotection potential

Balogh, Tatiana Santana
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/06/2011 Português
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Extratos vegetais glicólicos são amplamente utilizados em formulações cosméticas devido às várias atividades clínicas atribuídas aos mesmos. O presente trabalho teve por objetivo selecionar os seis extratos comerciais glicólicos não padronizados com maiores teores de polifenóis e flavonoides totais e com maior atividade antioxidante dentre doze extratos [açaí (Euterpe oleracea), acerola (Malpighia glabra L.), castanha da Índia (Aesculus hippocastanum L.), chá verde (Camellia sinensis), erva-mate (Ilex paraguariensis A. St. Hil), framboesa (Rubus idaeus L.), ginco (Ginkgo biloba L.), menta (Mentha piperita L.), morango (Fragaria vesca L.), própolis, romã (Punica granatum L.) e uva (Vitis vinifera L.)] para realização de Estudo da Estabilidade e avaliação in vitro da eficácia fotoprotetora dos mesmos. A dissertação foi dividida em três capítulos. No primeiro capítulo, os doze extratos glicólicos foram avaliados quanto à presença e teor de flavonoides e polifenóis totais, bem como, quanto à atividade antioxidante determinada por DPPH e ORAC. Os extratos de romã, erva-mate, menta, própolis, ginco e chá verde apresentaram os maiores teores de polifenóis e flavonoides totais. Assim, os mesmos foram selecionados para as etapas seguintes do estudo. O capítulo 2 apresentou o estudo da estabilidade...

Improving photoprotection of Beauveria bassiana conidia for biological control of the cactus pest Dactylopius opuntiae in the semiarid region northeast of Brazil

Santos, P. de S.; da Silva, M. A. Q.; Monteiro, A. C.; Gava, C. A. T.
Fonte: Taylor & Francis Ltd Publicador: Taylor & Francis Ltd
Tipo: Artigo de Revista Científica Formato: 893-902
Português
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); A technical grade conidial preparation of the entomopathogenic fungus Beauveria bassiana isolate LCB63 was exposed to ultraviolet light ( UV) from artificial and natural sources in the presence of various photoprotectants to develop a viable formulation to control Dactylopius opuntiae, a limiting pest of forage cacti in the Brazilian semiarid region. In the first experiment, Conidial viability was assessed in preparations containing water and liposoluble photoprotectants at a concentration of 1% and exposed to solar radiation for 0, 60, and 120 min. In another experiment, preparations containing different concentrations of the selected photoprotectants were exposed to natural and artificial UV radiation for 120 and 5 min, respectively. Insecticide activity of technical grade conidial preparations containing selected photoprotectants were evaluated against first instar nymphs of D. opuntiae. In general, no evaluated compounds showed deleterious effects on conidial germination, and they provided a strong degree of protection over a short period of time. One-percent concentrations of starch and skim milk resulted in low photoprotection over a longer irradiation period...

Photosynthetic activity, photoprotection and photoinhibition in intertidal microphytobenthos as studied in situ using variable chlorophyll fluorescence

Serôdio, João; Vieira, S.; Cruz, S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
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The photosynthetic activity of microphytobenthos biofilms was studied in situ on an intertidal mudflat of the Ria de Aveiro, Portugal. Time series of physical variables characterizing the microenvironment at the sediment photic zone (incident solar irradiance, temperature, salinity), photophysiological parameters and productive biomass of undisturbed microalgal assemblages were measured during daytime low-tide periods along one spring–neap tidal cycle, with the objective of (1) characterizing the short-term variability in photosynthetic activity in situ, (2) relating it with the changing environmental conditions and (3) with the operation of physiologically (xanthophyll cycle) and behaviorally (vertical migration) based photoprotective processes, and (4) assessing the occurrence of photoinhibition. Pulse Amplitude Modulated (PAM) fluorometry was applied to measure photosynthetic activity (the effective and maximum quantum yield of photosystem II, ΔF/Fm′ and Fv/Fm; the photosynthesis index EFY; rapid light-response curves (RLC)), the photoprotective operation of the xanthophyll cycle and photoinhibition (non-photochemical quenching, NPQ; quantum efficiency of open RCs, Fv′/Fm′), and vertical migration (productive biomass, Fo). The photosynthetic activity was found to be strongly affected by the cumulative light dose received during the morning low-tide periods. The fluorescence indices ΔF/Fm′...

Mechanisms of photoprotection and nonphotochemical quenching in pea light-harvesting complex at 2.5 Å resolution

Standfuss, Jörg; Terwisscha van Scheltinga, Anke C; Lamborghini, Matteo; Kühlbrandt, Werner
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 Å structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals the mutual arrangement of 42 chlorophylls a and b, 12 carotenoids and six lipids in the LHC-II trimer. Spectral assignment of individual chlorophylls indicates the flow of energy in the complex and the mechanism of photoprotection in two close chlorophyll a–lutein pairs. We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat. Our structure shows the complex in a quenched state, which may be relevant for the rapid, pH-induced component of nonphotochemical quenching.

Photoprotection of human retinal pigment epithelium cells against blue light-induced apoptosis by melanin free radicals from Sepia officinalis

Seagle, Brandon-Luke L.; Gasyna, Elzbieta M.; Mieler, William F.; Norris, James R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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Cultured retinal pigment epithelium (RPE) cells can phagocytize large foreign particles. Heterogeneous melanin aggregates from Sepia officinalis, a species of cuttlefish, were fed to cultured human RPE cells to produce cells laden with Sepia melanin. Blue light-induced apoptosis (BLIA) assays were performed by flow cytometry on parallel cultures consisting of RPE cells isolated from independent eyes and evenly divided into two cultures, one fed Sepia melanin and one containing only native melanin. After culturing and growth of the cells under blue light illumination for 7 days, the apoptosis percentage of all cultures indicated that Sepia feeding significantly reduced BLIA. To account for Sepia photoprotection, continuous-wave EPR and time-resolved EPR experiments were performed with parallel RPE cultures by using UV (355 nm) and green (532 nm) laser irradiation. Continuous-wave EPR spectra prove that the concentrations of intrinsic and extrinsic melanin free radicals in the Sepia–RPE culture are large compared with those concentrations in the RPE culture. Time-resolved EPR spectra indicate that both UV and green light produced extrinsic melanin radicals as radical pairs from the triplet manifold with a linear dependence on the number of photons per second. These experiments conclusively demonstrate that decreased RPE susceptibility to BLIA correlates with increased intracellular melanin free radical concentrations and that nonnative melanin can supplement native melanin photoprotection of RPE cells.

Triplet Exciton Formation as a Novel Photoprotection Mechanism in Chlorosomes of Chlorobium tepidum

Kim, Hanyoup; Li, Hui; Maresca, Julia A.; Bryant, Donald A.; Savikhin, Sergei
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Português
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Chlorosomes comprise thousands of bacteriochlorophylls (BChl c, d, or e) in a closely packed structure surrounded by a lipid-protein envelope and additionally contain considerable amounts of carotenoids, quinones, and BChl a. It has been suggested that carotenoids in chlorosomes provide photoprotection by rapidly quenching triplet excited states of BChl via a triplet-triplet energy transfer mechanism that prevents energy transfer to oxygen and the formation of harmful singlet oxygen. In this work we studied triplet energy transfer kinetics and photodegradation of chlorosomes isolated from wild-type Chlorobium tepidum and from genetically modified species with different types of carotenoids and from a carotenoid-free mutant. Supporting a photoprotective function of carotenoids, carotenoid-free chlorosomes photodegrade ∼3 times faster than wild-type chlorosomes. However, a significant fraction of the BChls forms a long-lived, triplet-like state that does not interact with carotenoids or with oxygen. We propose that these states are triplet excitons that form due to triplet-triplet interaction between the closely packed BChls. Numerical exciton simulations predict that the energy of these triplet excitons may fall below that of singlet oxygen and triplet carotenoids; this would prevent energy transfer from triplet BChl. Thus...

The Role of the Vitamin D Receptor and ERp57 in Photoprotection by 1α,25-Dihydroxyvitamin D3

Sequeira, Vanessa B.; Rybchyn, Mark S.; Tongkao-on, Wannit; Gordon-Thomson, Clare; Malloy, Peter J.; Nemere, Ilka; Norman, Anthony W.; Reeve, Vivienne E.; Halliday, Gary M.; Feldman, David; Mason, Rebecca S.
Fonte: Endocrine Society Publicador: Endocrine Society
Tipo: Artigo de Revista Científica
Português
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UV radiation (UVR) is essential for formation of vitamin D3, which can be hydroxylated locally in the skin to 1α,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Recent studies implicate 1,25-(OH)2D3 in reduction of UVR-induced DNA damage, particularly thymine dimers. There is evidence that photoprotection occurs through the steroid nongenomic pathway for 1,25-(OH)2D3 action. In the current study, we tested the involvement of the classical vitamin D receptor (VDR) and the endoplasmic reticulum stress protein 57 (ERp57), in the mechanisms of photoprotection. The protective effects of 1,25-(OH)2D3 against thymine dimers were abolished in fibroblasts from patients with hereditary vitamin D-resistant rickets that expressed no VDR protein, indicating that the VDR is essential for photoprotection. Photoprotection remained in hereditary vitamin D-resistant rickets fibroblasts expressing a VDR with a defective DNA-binding domain or a mutation in helix H1 of the classical ligand-binding domain, both defects resulting in a failure to mediate genomic responses, implicating nongenomic responses for photoprotection. Ab099, a neutralizing antibody to ERp57, and ERp57 small interfering RNA completely blocked protection against thymine dimers in normal fibroblasts. Co-IP studies showed that the VDR and ERp57 interact in nonnuclear extracts of fibroblasts. 1...

Effects of stressing high PAR on mycosporine-like amino acids in the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

Torres, Priscila Bezerra; Ho, Fanly Fungyi Chow; Ferreira, Marcelo José Pena; Santos, Deborah Yara Alves Cursino dos
Fonte: Society for Medicinal Plant and Natural Product Research; Guimarães Publicador: Society for Medicinal Plant and Natural Product Research; Guimarães
Tipo: Conferência ou Objeto de Conferência
Português
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Studies in Rhodophyta species have been carried out to understand the mechanism of photoprotection against excessive photosynthetically active radiation (PAR). However, few studies concerning on the role of mycosporine-like amino acids (MAAs) in this mechanism have been developed. Thus, the aims of this study were to identify the MAAs in Gracilariopsis tenuifrons (C.J. and E.C Oliveira) Fredericq & Hommersand and understand the behavior of these compounds against the high PAR stress. To achieve these goals, apical tips of G. tenuifrons were cultivated at three PAR intensities (60, 600 and 1000µmol.m-2.s-1) for one week. The MAAs were identified and quantified by HPLC-MS and HPLC. Asterina-330, palythinol, palythene and usujirene were identified. Usujirene is an inedited MAA identified for this family and palythene is very unusual. Among these MAAs, only palythinol content increased about 3-fold in high light. This response may suggest that palythinol plays an important role in photoprotection in this alga. The role of MAAs in absorbing UV radiation and dissipate the excess of energy as harmless heat is well known. However, some of these compounds have been reported as PAR-dose dependent. Controversial results regarding palythinol amounts in red algae under high PAR intensities have been published. Although in Chondrus crispus (Gigartinales...

Brazilian Consensus on Photoprotection

Schalka, Sérgio; Steiner, Denise; Ravelli, Flávia Naranjo; Steiner, Tatiana; Terena, Aripuanã Cobério; Marçon, Carolina Reato; Ayres, Eloisa Leis; Addor, Flávia Alvim Sant'anna; Miot, Helio Amante; Ponzio, Humberto; Duarte, Ida; Neffá, Jane; da Cun
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians...

Brazilian Consensus on Photoprotection

Schalka,Sérgio; Steiner,Denise; Ravelli,Flávia Naranjo; Steiner,Tatiana; Terena,Aripuanã Cobério; Marçon,Carolina Reato; Ayres,Eloisa Leis; Addor,Flávia Alvim Sant'anna; Miot,Helio Amante; Ponzio,Humberto; Duarte,Ida; Neffá,Jane; Cunha,José Antôn
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 Português
Relevância na Pesquisa
27.574287%
Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8,500 km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians...

Knowledge, attitudes and practices about sun exposure and photoprotection in outpatients attending dermatology clinics at four hospitals in Lima, Peru

Thomas-Gavelan,Elizabeth; Sáenz-Anduaga,Eliana; Ramos,Willy; Sánchez-Saldaña,Leonardo; Sialer,María del Carmen
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
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BACKGROUND: To establish the knowledge, about sun exposure and photoprotection in outpatients treated at the dermatology clinics in four hospitals in Lima, Peru. MATERIAL AND METHODS: A cross-sectional study was conducted involving a sample of 364 patients selected using a systematic random sampling process in the four participating hospitals. The selected patients were interviewed to determine their knowledge, behavior and practices in relation to sun exposure and photoprotection. The chi-square test was used to identify any significant differences between knowledge and practices. RESULTS: The mean age of the patients in this sample was 45.1 ± 21.4 years. Of the 364 patients, 55.9% were women and 54.8% had skin phototype IV. The principal risks related to sun exposure were skin cancer (80.5%) and sunburn (77.8%). Knowledge regarding sun protection was more evident in individuals with university/college education (p<0.001). In addition, 78.9% of the individuals reported that they knew about photo-protectors and 52.3% stated that they used them regularly. In general, women were more knowledgeable regarding sun protection (p=0.001). Of the total number of users of photoprotection, 38.4% used these products daily, while 61.6% used them only occasionally. The use of photo-protectors differed significantly in accordance with the individual's education level (p<0.001). In the majority of cases there was a statistically significant difference between knowledge and practice with respect to solar protection. CONCLUSIONS: The level of awareness of the outpatients treated at the dermatology clinics in these four hospitals in Lima...

Bacteriochlorophyll e monomers, but not aggregates, sensitize singlet oxygen: implications for a self-photoprotection mechanism in chlorosomes.

Arellano, Juan B.; Melo, Thor Bernt; Borrego, Carles M.; Naqvi, K. Razi
Fonte: American Society for Photobiology Publicador: American Society for Photobiology
Tipo: Artículo Formato: 412592 bytes; application/pdf
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Sensitization of singlet delta oxygen (O2(1Δg)) by bacteriochlorophyll e (BChle) has been investigated to gain a better understanding of the photoprotection mechanism(s) operating in chlorosomes of green photosynthetic bacteria. The sensitization process has been studied in media where BChle forms monomers (acetone and aqueous solutions containing 0.5% Triton X-100 [TX]) and in systems where BChle aggregates, namely, aqueous solutions containing 0.003% monogalactosyl diglyceride (MGDG) and chlorosomes (control as well as hexanol perturbed) from Chlorobium phaeobacteroides strain CL1401. In Ar-purged acetone, BChle triplets (BChle†) have a lifetime of a few tens of microseconds; however, in air-saturated acetone, quenching of BChle† by ground-state oxygen (O2(3Σ−g)) and formation of O2(1Δg) take place. The O2(1Δg) so formed is susceptible to quenching by BChle0, a ground-state BChle molecule. A Stern–Volmer analysis reveals a linear fit between the decay rate of O2(1Δg) and the BChle concentration. The rate constants for the quenching of O2(1Δg) by BChle0 and for the deactivation of O2(1Δg) by the solvent come out to be kq= (1.4 ± 0.1) × 10^9 M−1 s−1 and k0= (18.5 ± 0.7) × 10^3 s−1, respectively. The absolute quantum yield of O2(1Δg) sensitization by BChle monomers is 0.65 ± 0.15 in air-saturated acetone. In aqueous phase...

Photosynthesis and photoprotection responses to water stress in the wild-extinct plant Lysimachia minoricensis

Galmés, Jeroni; Abadía Bayona, Anunciación; Medrano Gil, Hipólito; Flexas, Jaume
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 918459 bytes; application/pdf
Português
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10 pages, 4 figures, 3 tables.-- Printed version published Jul 2007.; Lysimachia minoricensis is an endemic species of the Balearic Islands that has become extinct in the wild, but persists in botanical gardens. Attempts of re-introducing the species into its natural habitat, which consisted in temporary dry streams, have failed. Low genetic variability has been reported for the garden individuals, suggesting that a reduced potential to adapt to environmental changes could be among the reasons for its extinction. In the present study, we particularly test whether photosynthesis and photoprotection responses of this species to water stress could help explaining the lack of success of this species in its natural habitat.; Plants of L. minoricensis were grown in pots in a growth chamber. Soil water depletion was imposed over 20 days by stopping irrigation. Early stomata closure was observed in response to soil water depletion while leaves desiccated progressively. Although net photosynthesis was low in irrigated plants, due to a remarkably low mesophyll conductance to CO2, substantial photosynthetic activity was kept at severe drought, where leaf relative water content was as low as 50%, suggesting that L. minoricensis is a very drought-tolerant species. In parallel with decreased photosynthesis...

Assessment of photoprotection mechanisms of grapevines at low temperature

Hendrickson, Luke; Ball, Marilyn; Osmond, C. Barry; Furbank, Robert Thomas; Chow, Wah S (Fred)
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica
Português
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The photosynthetic response of grapevine leaves (Vitis vinifera L. cv. Riesling) to low temperature was studied in the field and laboratory. Light-saturated rates of photosynthetic electron transport were lower and non-photochemical energy dissipation was higher when leaves were subject to low morning temperatures than to high afternoon temperatures under field conditions. These responses to low temperatures occurred without sustained reduction of quantum efficiency of PSII as measured by the variable to maximum chlorophyll fluorescence yield ratio, Fv/Fm, after dark adaptation. The temperature dependence of light-saturated apparent electron transport rate, gas exchange and non-photochemical quenching (NPQ) was also examined in laboratory experiments with glasshouse-grown material. NPQ reached saturation at lower light intensity with decreasing temperature. The relationship between the quantum efficiency of PSII and CO2 fixation at 25°C (2-21% O2) and 10°C (2-21% O2) indicated a decreased dependence of electron transport on both photorespiration and the Mehler reaction at the lower temperature. The calculated percentage of electron flow to the Mehler reaction declined faster than photorespiration at low temperature. Warm- and cold-treated leaf discs under saturating light showed very little photoinhibition as measured by sustained reduction in Fv/Fm...