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1.
Photochem Photobiol Sci ; 18(7): 1685-1699, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31166333

RESUMO

The UVR8 photoreceptor in Arabidopsis thaliana is specific for ultraviolet-B (UV-B; 280-315 nm) radiation and its activation leads to a number of UV-B acclimation responses, including the accumulation of flavonoids. UVR8 participates in a signaling cascade involving COP1 and HY5 so that the absence of any of these components results in a reduction in the ability of a plant to accumulate flavonoids in response to UV; Cop1 mutants show high dropouts and hy5-ks50 hyh double mutants show very low levels of flavonoids. The predominant phenolics in Arabidopsis thaliana are sinapic acid derivatives as well as non-aclyated quercetin and kaempferol di- and triglycosides containing glucose and rhamnose as glycosylated sugar moieties. How this flavonoid profile in Arabidopsis thaliana is affected by UV radiation, how rapidly these changes occur in changing UV conditions, and which components of the UV-B signalling pathway are involved in rapid UV acclimatization reactions is poorly understood. In the present study, we examined these questions by characterizing the flavonoid profiles of Arabidopsis thaliana signalling mutants and wild types grown under different UV levels of constant UV-B+PAR ratios and then transferring a subset of plants to alternate UV conditions. Results indicate that flavonoid accumulation in Arabidopsis thaliana is triggered by UV and this response is amplified by higher levels of UV but not by all compounds to the same extent. The catechol structure in quercetin seems to be less important than the glycosylation pattern, e.g. having 2 rhamnose moieties in determining responsivity. At low UV+PAR intensities the introduction of UV leads to an initial tendency of increase of flavonoids in the wild types that was detected after 3 days. It took 7 days for these changes to be detected in plants grown under high UV+PAR intensities suggesting a priming of PAR. Thus, the flavonoid profile in Arabidopsis thaliana is altered over time following exposure to UV and PAR, but the functional significance of these changes is currently unclear.


Assuntos
Arabidopsis/efeitos da radiação , Flavonoides/metabolismo , Transdução de Sinais/efeitos da radiação , Raios Ultravioleta , Arabidopsis/química , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Cromatografia Líquida de Alta Pressão , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ligação a DNA , Flavonoides/análise , Mutagênese , Folhas de Planta/química , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Espectrometria de Massas por Ionização por Electrospray , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo
2.
Sci Total Environ ; 682: 239-246, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31121350

RESUMO

Aquatic and terrestrial organisms are being exposed to a number of anthropogenically-induced environmental stresses as a consequence of climate change. In addition, climate change is altering various linkages that exist between ecosystems on land and in water. Here we compare and contrast how climate change is altering aquatic and terrestrial environments and address some of the ways that the organisms in these ecosystems, especially the primary producers, are being affected by climate change factors, including changes in temperature, moisture, atmospheric carbon dioxide and solar UV radiation. Whereas there are some responses to climate change in common between terrestrial and aquatic ecosystems (e.g., changes in species composition and shifting geographic ranges and distributions), there are also responses that fundamentally differ between these two (e.g., responses to UV radiation). Climate change is also disrupting land-water connections in ways that influence biogeochemical and hydrologic cycles, and biosphere-atmosphere interactions in ways that can modify how aquatic and terrestrial ecosystems are affected by climate change and can influence climate change. The effects of climate change on these ecosystems are having wide-ranging effects on ecosystem biodiversity, structure and function and the abilities of these systems to provide essential services.


Assuntos
Mudança Climática , Ecossistema , Biodiversidade
3.
Photochem Photobiol Sci ; 18(3): 681-716, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30810560

RESUMO

Exposure of plants and animals to ultraviolet-B radiation (UV-B; 280-315 nm) is modified by stratospheric ozone dynamics and climate change. Even though stabilisation and projected recovery of stratospheric ozone is expected to curtail future increases in UV-B radiation at the Earth's surface, on-going changes in climate are increasingly exposing plants and animals to novel combinations of UV-B radiation and other climate change factors (e.g., ultraviolet-A and visible radiation, water availability, temperature and elevated carbon dioxide). Climate change is also shifting vegetation cover, geographic ranges of species, and seasonal timing of development, which further modifies exposure to UV-B radiation. Since our last assessment, there has been increased understanding of the underlying mechanisms by which plants perceive UV-B radiation, eliciting changes in growth, development and tolerances of abiotic and biotic factors. However, major questions remain on how UV-B radiation is interacting with other climate change factors to modify the production and quality of crops, as well as important ecosystem processes such as plant and animal competition, pest-pathogen interactions, and the decomposition of dead plant matter (litter). In addition, stratospheric ozone depletion is directly contributing to climate change in the southern hemisphere, such that terrestrial ecosystems in this region are being exposed to altered patterns of precipitation, temperature and fire regimes as well as UV-B radiation. These ozone-driven changes in climate have been implicated in both increases and reductions in the growth, survival and reproduction of plants and animals in Antarctica, South America and New Zealand. In this assessment, we summarise advances in our knowledge of these and other linkages and effects, and identify uncertainties and knowledge gaps that limit our ability to fully evaluate the ecological consequences of these environmental changes on terrestrial ecosystems.


Assuntos
Mudança Climática , Ozônio Estratosférico/análise , Raios Ultravioleta , Animais , Dióxido de Carbono/análise , Ecossistema , Poluentes Ambientais/análise , Água Doce/análise , Aquecimento Global , Proliferação Nociva de Algas/efeitos da radiação , Luz , Modelos Químicos , Recursos Naturais , Fotólise/efeitos da radiação , Água do Mar/análise
4.
Photochem Photobiol Sci ; 18(5): 970-988, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30720036

RESUMO

Plants perceive ultraviolet-B (UV-B) radiation through the UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8), and initiate regulatory responses via associated signalling networks, gene expression and metabolic pathways. Various regulatory adaptations to UV-B radiation enable plants to harvest information about fluctuations in UV-B irradiance and spectral composition in natural environments, and to defend themselves against UV-B exposure. Given that UVR8 is present across plant organs and tissues, knowledge of the systemic signalling involved in its activation and function throughout the plant is important for understanding the context of specific responses. Fine-scale understanding of both UV-B irradiance and perception within tissues and cells requires improved application of knowledge about UV-attenuation in leaves and canopies, warranting greater consideration when designing experiments. In this context, reciprocal crosstalk among photoreceptor-induced pathways also needs to be considered, as this appears to produce particularly complex patterns of physiological and morphological response. Through crosstalk, plant responses to UV-B radiation go beyond simply UV-protection or amelioration of damage, but may give cross-protection over a suite of environmental stressors. Overall, there is emerging knowledge showing how information captured by UVR8 is used to regulate molecular and physiological processes, although understanding of upscaling to higher levels of organisation, i.e. organisms, canopies and communities remains poor. Achieving this will require further studies using model plant species beyond Arabidopsis, and that represent a broad range of functional types. More attention should also be given to plants in natural environments in all their complexity, as such studies are needed to acquire an improved understanding of the impact of climate change in the context of plant-UV responses. Furthermore, broadening the scope of experiments into the regulation of plant-UV responses will facilitate the application of UV radiation in commercial plant production. By considering the progress made in plant-UV research, this perspective highlights prescient topics in plant-UV photobiology where future research efforts can profitably be focussed. This perspective also emphasises burgeoning interdisciplinary links that will assist in understanding of UV-B effects across organisational scales and gaps in knowledge that need to be filled so as to achieve an integrated vision of plant responses to UV-radiation.


Assuntos
Folhas de Planta/metabolismo , Plantas/metabolismo , Raios Ultravioleta , Fenômenos Ecológicos e Ambientais
5.
PLoS One ; 14(2): e0210470, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30716078

RESUMO

Dryland ecosystems cover nearly 45% of the Earth's land area and account for large proportions of terrestrial net primary production and carbon pools. However, predicting rates of plant litter decomposition in these vast ecosystems has proven challenging due to their distinctly dry and often hot climate regimes, and potentially unique physical drivers of decomposition. In this study, we elucidated the role of photopriming, i.e. exposure of standing dead leaf litter to solar radiation prior to litter drop that would chemically change litter and enhance biotic decay of fallen litter. We exposed litter substrates to three different UV radiation treatments simulating three-months of UV radiation exposure in southern New Mexico: no light, UVA+UVB+Visible, and UVA+Visible. There were three litter types: mesquite leaflets (Prosopis glandulosa, litter with high nitrogen (N) concentration), filter paper (pure cellulose), and basswood (Tilia spp, high lignin concentration). We deployed the photoprimed litter in the field within a large scale precipitation manipulation experiment: ∼50% precipitation reduction, ∼150% precipitation addition, and ambient control. Our results revealed the importance of litter substrate, particularly N content, for overall decomposition in drylands, as neither filter paper nor basswood exhibited measurable mass loss over the course of the year-long study, while high N-containing mesquite litter exhibited potential mass loss. We saw no effect of photopriming on subsequent microbial decay. We did observe a precipitation effect on mesquite where the rate of decay was more rapid in ambient and precipitation addition treatments than in the drought treatment. Overall, we found that precipitation and N played a critical role in litter mass loss. In contrast, photopriming had no detected effects on mass loss over the course of our year-long study. These results underpin the importance of biotic-driven decomposition, even in the presence of photopriming, for understanding litter decomposition and biogeochemical cycles in drylands.


Assuntos
Folhas de Planta/efeitos da radiação , Plantas/efeitos da radiação , Prosopis/efeitos da radiação , Tilia/efeitos da radiação , Celulose/metabolismo , Clima Desértico , Ecossistema , Lignina/metabolismo , New Mexico , Nitrogênio/metabolismo , Folhas de Planta/fisiologia , Fenômenos Fisiológicos Vegetais/efeitos da radiação , Prosopis/fisiologia , Tilia/fisiologia , Raios Ultravioleta
6.
Front Plant Sci ; 8: 1451, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28878792

RESUMO

Ongoing changes in Earth's climate are shifting the elevation ranges of many plant species with non-native species often experiencing greater expansion into higher elevations than native species. These climate change-induced shifts in distributions inevitably expose plants to novel biotic and abiotic environments, including altered solar ultraviolet (UV)-B (280-315 nm) radiation regimes. Do the greater migration potentials of non-native species into higher elevations imply that they have more effective UV-protective mechanisms than native species? In this study, we surveyed leaf epidermal UV-A transmittance (TUV A) in a diversity of plant species representing different growth forms to test whether native and non-native species growing above 2800 m elevation on Mauna Kea, Hawaii differed in their UV screening capabilities. We further compared the degree to which TUV A varied along an elevation gradient in the native shrub Vaccinium reticulatum and the introduced forb Verbascum thapsus to evaluate whether these species differed in their abilities to adjust their levels of UV screening in response to elevation changes in UV-B. For plants growing in the Mauna Kea alpine/upper subalpine, we found that adaxial TUV A, measured with a UVA-PAM fluorometer, varied significantly among species but did not differ between native (mean = 6.0%; n = 8) and non-native (mean = 5.8%; n = 11) species. When data were pooled across native and non-native taxa, we also found no significant effect of growth form on TUV A, though woody plants (shrubs and trees) were represented solely by native species whereas herbaceous growth forms (grasses and forbs) were dominated by non-native species. Along an elevation gradient spanning 2600-3800 m, TUV A was variable (mean range = 6.0-11.2%) and strongly correlated with elevation and relative biologically effective UV-B in the exotic V. thapsus; however, TUV A was consistently low (3%) and did not vary with elevation in the native V. reticulatum. Results indicate that high levels of UV protection occur in both native and non-native species in this high UV-B tropical alpine environment, and that flexibility in UV screening is a mechanism employed by some, but not all species to cope with varying solar UV-B exposures along elevation gradients.

7.
Artigo em Inglês | MEDLINE | ID: mdl-28140763

RESUMO

Phenylbutazone is a non-steroidal anti-inflammatory drug licensed for use in horses to treat musculoskeletal disorders. It is not permitted in the European Union for use in animals destined for the food chain. Official statistics provided by the European Food Safety Authority (EFSA) show that 0.18% of bovines tested in the European Union between 2008 and 2014 for non-steroidal anti-inflammatory drugs were non-compliant, with phenylbutazone representing over 28% of these. Anecdotal evidence suggests animals that have not been treated with the drug may have produced non-compliant samples, possibly through some form of contamination. In this study, ultra-high-performance liquid chromatography coupled with mass-spectrometric detection was applied to bovine plasma samples to determine if detectable residues (CCα = 0.28 ng ml-1) may occur in untreated animals as a result of environmental contamination through normal farming practice. The study demonstrates that waste from animals treated with phenylbutazone, and spread on an area of pasture, can contaminate untreated bovines grazing the pasture many weeks later. It was determined that this contamination, which can persist over a significant period, may be due to the ingestion of as little as 30 µg phenylbutazone by a 500 kg bullock.


Assuntos
Anti-Inflamatórios não Esteroides/sangue , Resíduos de Drogas/análise , Poluição Ambiental/análise , Fenilbutazona/sangue , Drogas Veterinárias/sangue , Animais , Anti-Inflamatórios não Esteroides/administração & dosagem , Bovinos , Cromatografia Líquida de Alta Pressão , Controle de Medicamentos e Entorpecentes/legislação & jurisprudência , Contaminação de Alimentos/análise , Herbivoria/fisiologia , Cavalos , Masculino , Fenilbutazona/administração & dosagem , Recomendações Nutricionais/legislação & jurisprudência , Espectrometria de Massas em Tandem , Reino Unido , Drogas Veterinárias/administração & dosagem
8.
Artigo em Inglês | MEDLINE | ID: mdl-27662433

RESUMO

Tetrodotoxin (TTX) is an emerging toxin in the European marine environment. It has various known structural analogues. It acts as a sodium channel blocker; the ability of each analogue to bind to the sodium channel varies with the particular structure of each analogue. Thus, each analogue will vary in its toxic potential. TTX analogues co-occur in food samples at variable concentrations. An LC-MS method was developed for the identification and quantitation of several analogues of TTX using an LTQ-Orbitrap XL mass spectrometer. The LTQ-Orbitrap XL mass spectrometer facilitates high mass accuracy measurement up to 100,000 full width at half maximum (FWHM). Using high resolution at 100,000 FWHM allows for the identification of TTX and its analogues in various matrices, including puffer fish and molluscan shellfish samples (Δ ppm = 0.28-3.38). The confirmation of characteristic fragment ions of TTX and its analogues was achieved by determining their elemental formulae via high mass accuracy. A quantitative method was then developed and optimised using these characteristic fragment ions. The limit of quantitation (LOQ) of the method was 0.136 µg g(-1) (S/N = 10) and the limit of detection (LOD) was 0.041 µg g(-1) (S/N = 3) spiking TTX standard into TTX-free mackerel fish extracts. The method was applied to naturally contaminated puffer fish and molluscan shellfish samples to confirm the presence of TTX and its analogues.


Assuntos
Frutos do Mar/análise , Tetraodontiformes , Tetrodotoxina/análogos & derivados , Tetrodotoxina/análise , Animais , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas , Conformação Molecular , Tetrodotoxina/química
9.
Artigo em Inglês | MEDLINE | ID: mdl-27619502

RESUMO

Tetrodotoxin (TTX), often referred to as the 'puffer fish' poison, is a marine toxin and it has been identified as the agent responsible for many food poisoning incidents around the world. It is a neurotoxin that blocks voltage-gated sodium channels, resulting in respiratory paralysis and even death in severe cases. It is known to occur in many different species of fish and other organisms. The toxin is mainly found in the Southeast Asia region. Worryingly, TTX is starting to appear in European waters. It is suspected that this is a consequence of Lessepsian migration, also known as the Erythrean invasion. Therefore, straightforward and reliable extraction and analytical methods are now urgently required to monitor seafood of European origin for TTX. This paper provides a versatile, dependable and robust method for the analysis of TTX in puffer fish and trumpet shellfish using LC-MS/MS. A three-stage approach was implemented involving: (1) the screening of samples using fast multiple reaction monitoring (MRM) mass spectral analysis to identify quickly positive samples on a triple quadrupole mass spectrometer (QqQMS/MS), the API 3000; (2) a Fourier-transform (FT)-MS full-scan analysis of positive samples to collect qualitative data; and (3) a method with a longer chromatography run to identify and quantitate the positive samples using the QqQMS. The quantitative LC-QqQMS method delivered excellent linearity for solvent-based standards (0.01-7.5 µg ml-1; R2 ≥ 0.9968) as well as for matrix-matched standards (0.05-37.50 µg g-1; R2 ≥ 0.9869). Good inter-day repeatability was achieved for all the relevant analytes with %RSD values (n = 9) ranging from 1.11% to 4.97% over a concentration range of 0.01-7.5 µg ml-1. A sample clean-up procedure for the puffer fish and trumpet shellfish was developed to ensure acceptable and reproducible recoveries to enable accurate and precise determination of TTX in a myriad of tissues types. Blank mackerel matrix was used for the TTX standard spiking studies in order to calculate the recoveries of the toxin during the extraction procedure. The recovery was 61.17% ± 5.42% for the extraction protocol. MS/MS studies were performed on a linear-trap quadruple-Orbitrap mass spectrometer (LTQ-Orbitrap) to obtain high-mass-accuracy data of the target analytes and their characteristic fragment ions in the puffer fish and trumpet shellfish samples. This facilitated identification of TTX and its associated analogues. These high-mass-accuracy studies facilitated the development of a rapid MRM-based quantitative method for TTX determination on the LC-QqQMS.


Assuntos
Tetrodotoxina/análise , Animais , Cromatografia Líquida , Peixes , Espectrometria de Massas
10.
Oecologia ; 181(1): 55-63, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26809621

RESUMO

The accumulation of ultraviolet (UV)-absorbing compounds (flavonoids and related phenylpropanoids) in the epidermis of higher plants reduces the penetration of solar UV radiation to underlying tissues and is a primary mechanism of acclimation to changing UV conditions resulting from ozone depletion and climate change. Previously we reported that several herbaceous plant species were capable of rapid, diurnal adjustments in epidermal UV transmittance (T UV), but how widespread this phenomenon is among plants has been unknown. In the present study, we tested the generality of this response by screening 37 species of various cultivated and wild plants growing in four locations spanning a gradient of ambient solar UV and climate (Hawaii, Utah, Idaho and Louisiana). Non-destructive measurements of adaxial T UV indicated that statistically significant midday decreases in T UV occurred in 49 % of the species tested, including both herbaceous and woody growth forms, and there was substantial interspecific variation in the magnitude of these changes. In general, plants in Louisiana exhibited larger diurnal changes in T UV than those in the other locations. Moreover, across all taxa, the magnitude of these changes was positively correlated with minimum daily air temperatures but not daily UV irradiances. Results indicate that diurnal changes in UV shielding are widespread among higher plants, vary both within and among species and tend to be greatest in herbaceous plants growing in warm environments. These findings suggest that plant species differ in their UV protection "strategies" though the functional and ecological significance of this variation in UV sunscreen protection remains unclear at present.


Assuntos
Aclimatação , Flavonoides/metabolismo , Fenóis/metabolismo , Epiderme Vegetal/metabolismo , Plantas/metabolismo , Raios Ultravioleta , Clima , Mudança Climática , Ozônio , Propanóis/metabolismo , Especificidade da Espécie , Luz Solar , Protetores Solares , Temperatura , Estados Unidos
11.
Plant Cell Environ ; 39(1): 222-30, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26177782

RESUMO

The accumulation of ultraviolet (UV)-absorbing compounds (flavonoids and related phenylpropanoids) and the resultant decrease in epidermal UV transmittance (TUV ) are primary protective mechanisms employed by plants against potentially damaging solar UV radiation and are critical components of the overall acclimation response of plants to changing solar UV environments. Whether plants can adjust this UV sunscreen protection in response to rapid changes in UV, as occurs on a diurnal basis, is largely unexplored. Here, we use a combination of approaches to demonstrate that plants can modulate their UV-screening properties within minutes to hours, and these changes are driven, in part, by UV radiation. For the cultivated species Abelmoschus esculentus, large (30-50%) and reversible changes in TUV occurred on a diurnal basis, and these adjustments were associated with changes in the concentrations of whole-leaf UV-absorbing compounds and several quercetin glycosides. Similar results were found for two other species (Vicia faba and Solanum lycopersicum), but no such changes were detected in Zea mays. These findings reveal a much more dynamic UV-protection mechanism than previously recognized, raise important questions concerning the costs and benefits of UV-protection strategies in plants and have practical implications for employing UV to enhance crop vigor and quality in controlled environments.


Assuntos
Abelmoschus/efeitos da radiação , Flavonoides/efeitos da radiação , Hibiscus/efeitos da radiação , Lycopersicon esculentum/efeitos da radiação , Vicia faba/efeitos da radiação , Zea mays/efeitos da radiação , Abelmoschus/fisiologia , Aclimatação , Ritmo Circadiano , Flavonoides/fisiologia , Hibiscus/fisiologia , Lycopersicon esculentum/fisiologia , Epiderme Vegetal/fisiologia , Epiderme Vegetal/efeitos da radiação , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Luz Solar , Raios Ultravioleta , Vicia faba/fisiologia , Zea mays/fisiologia
12.
Inorg Chem ; 54(18): 9027-32, 2015 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-26357956

RESUMO

We report the dramatic increase of the Seebeck coefficient S and thermoelectric performance of calcium cobaltite Ca3Co4O9+δ ceramics through non-stoichiometric addition of minute amount of Ba. The nominal chemistry of polycrystal pellets are Ca3BaxCo4O9+δ (x = 0, 0.01, 0.05, and 0.1). At 323 K, S of Ca3Co4O9+δ is 135 µV K(-1), whereas S of Ba incorporated Ca3Ba0.05Co4O9+δ is 162.5 µV·K(-1), which is the highest S value near room temperature regime reported for calcium cobaltite. The increase of S for Ca3Ba0.05Co4O9+δ sample is accompanied by the decrease of the electrical resistivity ρ, resulting in high power factor S(2)/ρ of 843 µW·m(-1) K(-2) at 1007 K. Moreover, the thermal conductivities κ of Ca3BaxCo4O9+δ decrease with the increase of the Ba addition. The figure-of-merit ZT for Ca3Ba0.05Co4O9+δ reaches 0.52 at 1073 K and a factor of 2.5 increment in comparison with undoped Ca3Co4O9+δ. Nanostructure examinations show that the added Ba segregated at the Ca3Co4O9+δ grain boundaries, while the Ca3Co4O9+δ grain interior is free of Ba. Performance enhancement is attributed to the carrier filtering effect caused by the Ba segregation. In addition, Ba segregation promotes the better crystal alignment and the development of crystal texture.

13.
Plant Physiol Biochem ; 93: 94-100, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25465528

RESUMO

The accumulation of UV-absorbing compounds (flavonoids and other phenylpropanoid derivatives) and resultant decrease in the UV transmittance of the epidermis in leaves (TUV), is a primary protective mechanism against the potentially deleterious effects of UV radiation and is a critical component of the overall acclimation response of plants to changing UV environments. Traditional measurements of TUV were laborious, time-consuming and destructive or invasive, thus limiting their ability to efficiently make multiple measurements of the optical properties of plants in the field. The development of rapid, nondestructive optical methods of determining TUV has permitted the examination of UV optical properties of leaves with increased replication, on a finer time scale, and enabled repeated sampling of the same leaf over time. This technology has therefore allowed for studies examining acclimation responses to UV in plants in ways not previously possible. Here we provide a brief review of these earlier studies examining leaf UV optical properties and some of their important contributions, describe the principles by which the newer non-invasive measurements of epidermal UV transmittance are made, and highlight several case studies that reveal how this technique is providing new insights into this UV acclimation response in plants, which is far more plastic and dynamic than previously thought.


Assuntos
Aclimatação/efeitos da radiação , Epiderme Vegetal/metabolismo , Folhas de Planta/metabolismo , Fenômenos Fisiológicos Vegetais/efeitos da radiação , Raios Ultravioleta , Aclimatação/genética , Epiderme Vegetal/genética , Folhas de Planta/genética , Fenômenos Fisiológicos Vegetais/genética
15.
Anal Bioanal Chem ; 405(24): 7753-63, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23812877

RESUMO

Tetrodotoxin (TTX) is a potent neurotoxin emerging in European waters due to increasing ocean temperatures. Its detection in seafood is currently performed as a consequence of using the Association of Analytical Communities (AOAC) mouse bioassay (MBA) for paralytic shellfish poisoning (PSP) toxins, but TTX is not monitored routinely in Europe. Due to ethical and performance-related issues associated with this bioassay, the European Commission has recently published directives extending procedures that may be used for official PSP control. An AOAC-accredited high-performance liquid chromatography (HPLC) method has now been accepted by the European Union as a first action screening method for PSP toxins to replace the MBA. However, this AOAC HPLC method is not capable of detecting TTX, so this potent toxin would be undetected; thereby, a separate method of analysis is required. Surface plasmon resonance (SPR) optical biosensor technology has been proven as a potential alternative screening method to detect PSP toxins in seafood. The addition of a similar SPR inhibition assay for TTX would complement the PSP assay in removing the MBA. The present report describes the development and single laboratory validation in accordance with AOAC and IUPAC guidelines of an SPR method to be used as a rapid screening tool to detect TTX in the sea snail Charonia lampas lampas, a species which has been implicated in 2008 in the first case of human TTX poisoning in Europe. As no current regulatory limits are set for TTX in Europe, single laboratory validation was undertaken using those for PSP toxins at 800 µg/kg. The decision limit (CCα) was 100 µg/kg, with the detection capability (CCß) found to be ≤200 µg/kg. Repeatability and reproducibility were assessed at 200, 400, and 800 µg/kg and showed relative standard deviations of 8.3, 3.8, and 5.4% and 7.8, 8.3, and 3.7% for both parameters at each level, respectively. At these three respective levels, the recovery of the assay was 112, 98, and 99%.


Assuntos
Bioensaio/métodos , Inocuidade dos Alimentos/métodos , Frutos do Mar , Tetrodotoxina/análise , Animais , Europa (Continente) , Humanos , Limite de Detecção , Camundongos , Modelos Moleculares , Óptica e Fotônica , Fatores de Risco , Tetrodotoxina/química
16.
Physiol Plant ; 149(2): 200-13, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23330642

RESUMO

Epidermal UV transmittance (TUV ) and UV-absorbing compounds were measured in sun and shade leaves of Populus tremuloides and Vicia faba exposed to contrasting light environments under field conditions to evaluate UV acclimation potentials and regulatory roles of photosynthetically active radiation (PAR) and UV in UV-shielding. Within a natural canopy of P. tremuloides, TUV ranged from 4 to 98% and showed a strong nonlinear relationship with mid-day horizontal fluxes of PAR [photon flux density (PFD) = 6-1830 µmol m⁻² s⁻¹]; similar patterns were found for V. faba leaves that developed under a comparable PFD range. A series of field transfer experiments using neutral-density shade cloth and UV blocking/transmitting films indicated that PAR influenced TUV during leaf development to a greater degree than UV, and shade leaves of both species increased their UV-shielding when exposed to full sun; however, this required the presence of UV, with both UV-A and UV-B required for full acclimation. TUV of sun leaves of both species was largely unresponsive to shade either with or without UV. In most, but not all cases, changes in TUV were associated with alterations in the concentration of whole-leaf UV-absorbing compounds. These results suggest that, (1) moderate-to-high levels of PAR alone during leaf development can induce substantial UV-protection in field-grown plants, (2) mature shade leaves have the potential to adjust their UV-shielding which may reduce the detrimental effects of UV that could occur following sudden exposures to high light and (3) under field conditions, PAR and UV play different roles in regulating UV-shielding during and after leaf development.


Assuntos
Epiderme Vegetal/fisiologia , Folhas de Planta/fisiologia , Populus/fisiologia , Vicia faba/fisiologia , Clorofila/química , Clorofila/metabolismo , Relação Dose-Resposta à Radiação , Ecossistema , Fluorescência , Epiderme Vegetal/efeitos da radiação , Folhas de Planta/efeitos da radiação , Populus/efeitos da radiação , Luz Solar , Raios Ultravioleta , Vicia faba/efeitos da radiação
17.
Food Chem ; 136(3-4): 1584-9, 2013 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-23194566

RESUMO

Tetrodotoxin (TTX) is one of the most potent marine neurotoxins reported. The global distribution of this toxin is spreading with the European Atlantic coastline now being affected. Climate change and increasing pollution have been suggested as underlying causes for this. In the present study, two different sample preparation techniques were used to extract TTX from Trumpet shells and pufferfish samples. Both extraction procedures (accelerated solvent extraction (ASE) and a simple solvent extraction) were shown to provide good recoveries (80-92%). A UPLC-MS/MS method was developed for the analysis of TTX and validated following the guidelines contained in the Commission Decision 2002/657/EC for chemical contaminant analysis. The performance of this procedure was demonstrated to be fit for purpose. This study is the first report on the use of ASE as a mean for TTX extraction, the use of UPLC-MS/MS for TTX analysis, and the validation of this method for TTX in gastropods.


Assuntos
Métodos Analíticos de Preparação de Amostras/métodos , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas em Tandem/métodos , Tetrodotoxina/análise , Tetrodotoxina/isolamento & purificação , Animais , Gastrópodes , Tetraodontiformes
18.
J Synchrotron Radiat ; 19(Pt 4): 471-7, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22713876

RESUMO

A new data collection strategy for performing synchrotron energy-dispersive X-ray diffraction computed tomography has been devised. This method is analogous to angle-dispersive X-ray diffraction whose diffraction signal originates from a line formed by intersection of the incident X-ray beam and the sample. Energy resolution is preserved by using a collimator which defines a small sampling voxel. This voxel is translated in a series of parallel straight lines covering the whole sample and the operation is repeated at different rotation angles, thus generating one diffraction pattern per translation and rotation step. The method has been tested by imaging a specially designed phantom object, devised to be a demanding validator for X-ray diffraction imaging. The relative strengths and weaknesses of the method have been analysed with respect to the classic angle-dispersive technique. The reconstruction accuracy of the method is good, although an absorption correction is required for lower energy diffraction because of the large path lengths involved. The spatial resolution is only limited to the width of the scanning beam owing to the novel collection strategy. The current temporal resolution is poor, with a scan taking several hours. The method is best suited to studying large objects (e.g. for engineering and materials science applications) because it does not suffer from diffraction peak broadening effects irrespective of the sample size, in contrast to the angle-dispersive case.

20.
Chem Commun (Camb) ; 47(7): 2143-5, 2011 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-21165478

RESUMO

Hydrogen storage properties of Ti-doped nanosized (~20 nm) NaAlH(4) supported on carbon nanofibers were affected by the stage at which Ti was introduced. When Ti was deposited first followed by NaAlH(4), sorption properties were superior to the case where NaAlH(4) was deposited first followed by NaAlH(4). This was the result of both a smaller NaAlH(4) particle size and the more extensive catalytic action of Ti in the former material.

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