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排序方式: 共有258条查询结果,搜索用时 15 毫秒
51.
Ludmila Matos Baltazar Aimee E. Krausz Ana Camila Oliveira Souza Brandon L. Adler Angelo Landriscina Tagai Musaev Joshua D. Nosanchuk Adam J. Friedman 《PloS one》2015,10(3)
Antimicrobial photodynamic inhibition (aPI) utilizes radical stress generated from the excitation of a photosensitizer (PS) with light to destroy pathogens. Its use against Trichophyton rubrum, a dermatophytic fungus with increasing incidence and resistance, has not been well characterized. Our aim was to evaluate the mechanism of action of aPI against T. rubrum using curcumin as the PS in both free and nanoparticle (curc-np) form. Nanocarriers stabilize curcumin and allow for enhanced solubility and PS delivery. Curcumin aPI, at optimal conditions of 10 μg/mL of PS with 10 J/cm2 of blue light (417 ± 5 nm), completely inhibited fungal growth (p<0.0001) via induction of reactive oxygen (ROS) and nitrogen species (RNS), which was associated with fungal death by apoptosis. Interestingly, only scavengers of RNS impeded aPI efficacy, suggesting that curcumin acts potently via a nitrosative pathway. The curc-np induced greater NO• expression and enhanced apoptosis of fungal cells, highlighting curc-np aPI as a potential treatment for T. rubrum skin infections. 相似文献
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Maria J. Santos Hugo M. Matos Carla Baltazar Clara Grilo Margarida Santos-Reis 《Mammalian Biology》2009,74(6):448-455
Carnivores in Mediterranean ecosystems respond to the inherent heterogeneity of these systems by tracking the spatial and temporal availability of food resources. This feeding strategy, however, has been associated primarily with generalist carnivores and little is known for specialist species such as the European polecat. We collected polecat scat to determine the diet of this species, how it matches the seasonal availability of food resources, and how it is affected by population spatial structure and anthropogenic disturbance. Polecats were present in only 34% of the surveyed area and were clumped into three main population nuclei. Despite the spatial segregation of the populations, they had no significant differences in food items consumed. Polecats mostly fed on mammals (percentage of occurrence (P.O.)=43%) and arthropods (P.O.=49%). Biomass intake was also mostly from mammals (percentage of biomass (P.B.)=96%), followed by birds (P.B.=3%), with arthropods contributing less than 1%. Lagomorphs were the most consumed prey (P.O.=25% and P.B.=87%), which is consistent with the marked spatial overlap between scat with high content in lagomorphs and the areas with high wild rabbit availability. These results indicate that polecats are specialists in the consumption of wild rabbits, spatially track the availability of this prey, and may be affected by the decrease in abundance of the prey populations. Future conservation of polecats in Mediterranean regions of southern Portugal may be achieved through the restoration of hunted and diseased wild rabbit populations. 相似文献
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An overview of models of stomatal conductance at the leaf level 总被引:4,自引:0,他引:4
GAËLLE DAMOUR THIERRY SIMONNEAU HERVÉ COCHARD LAURENT URBAN 《Plant, cell & environment》2010,33(9):1419-1438
Stomata play a key role in plant adaptation to changing environmental conditions as they control both water losses and CO2 uptake. Particularly, in the context of global change, simulations of the consequences of drought on crop plants are needed to design more efficient and water‐saving cropping systems. However, most of the models of stomatal conductance (gs) developed at the leaf level link gs to environmental factors or net photosynthesis (Anet), but do not include satisfactorily the effects of drought, impairing our capacity to simulate plant functioning in conditions of limited water supply. The objective of this review was to draw an up‐to‐date picture of the gs models, from the empirical to the process‐based ones, along with their mechanistic or deterministic bases. It focuses on models capable to account for multiple environmental influences with emphasis on drought conditions. We examine how models that have been proposed for well‐watered conditions can be combined with those specifically designed to deal with drought conditions. Ideas for future improvements of gs models are discussed: the issue of co‐regulation of gs and Anet; the roles of CO2, absissic acid and H2O2; and finally, how to better address the new challenges arising from the issue of global change. 相似文献
57.
Background
The cell shape and morphology of plant tissues are intimately related to structural modifications in the primary cell wall that are associated with key processes in the regulation of cell growth and differentiation. The primary cell wall is composed mainly of cellulose immersed in a matrix of hemicellulose, pectin, lignin and some structural proteins. Xyloglucan is a hemicellulose polysaccharide present in the cell walls of all land plants (Embryophyta) and is the main hemicellulose in non-graminaceous angiosperms. 相似文献58.
Reis S Moutinho CG Matos C de Castro B Gameiro P Lima JL 《Analytical biochemistry》2004,334(1):117-126
In this work the critical micelle concentrations (cmc) of four bile salts, sodium cholate, sodium glycocholate, sodium deoxycholate, and sodium glycodeoxycholate, are determined and presented. Three independent noninvasive methodologies (potentiometry, derivative spectrophotometry, and light scattering) were used for cmc determination, at 25 degrees C with ionic strength adjusted to 0.10 M with NaCl. Spectrophotometric and potentiometric studies of some bile salts were also executed at various ionic strength values, thus allowing the influence of the ionic strength on the cmc value of the bile salt to be assessed. A critical comparison of the cmc values obtained with data collected from the literature is presented. Furthermore, this work makes an evaluation of the conceptual bases of different methodologies commonly used for cmc determination, since variations in the results obtained can be related mainly to different intrinsic features of the methods used (such as sensitivity or the need to include tracers or probes) or to the operational cmc definition applied. The undoubted definition of the experimental bile salt concentration that corresponds to cmc (operational cmc) is essential since in the case of these amphiphiles the formation of micelles is not as abrupt as in the case of ordinary association colloids. The biphasic nature of their aggregation leads to a "round-shaped" variation of the experimental parameters under analysis, which makes difficult the evaluation of the cmc values and can be responsible for the different results obtained. 相似文献
59.
Pedro J. Silva Baltazar de Castro W. R. Hagen 《Journal of biological inorganic chemistry》1999,4(3):284-291
The sulfhydrogenase complex of Pyrococcus furiosus is an αβγδ heterotetramer with both hydrogenase activity (borne by the αδ subunits) and sulfur reductase activity (carried
by the βγ subunits). The β-subunit contains at least two [4Fe-4S] cubanes and the γ-subunit contains one [2Fe-2S] cluster
and one FAD molecule. The δ-subunit contains three [4Fe-4S] cubanes and the α-subunit carries the NiFe dinuclear center. Only
three Fe/S signals are observed in EPR-monitored reduction by dithionite, NADPH, or internal substrate upon heating. All other
clusters presumably have reduction potentials well below that of the H+/H2 couple. Heat-induced reduction by internal substrate allows, for the first time, EPR monitoring of the NiFe center in a hyperthermophilic
hydrogenase, which passes through a number of states, some of which are similar to states previously defined for mesophilic
hydrogenases. The complexity of the observed transitions reflects a combination of temperature-dependent activation and temperature-dependent
reduction potentials.
Received: 10 December 1998 / Accepted: 16 February 1999 相似文献
60.
Galbeta1-3GalNAc (T-disaccharide) and related molecules were assayed to
describe the structural requirements of carbohydrates to bind Agaricus
bisporus lectin (ABL). Results provide insight into the most relevant
regions of T-disaccharide involved in the binding of ABL. It was found that
monosaccharides bind ABL weakly indicating a more extended
carbohydrate-binding site as compared to those involvedin the T-
disaccharide specific lectins such as jacalin and peanut agglutinin.
Lacto-N-biose (Galbeta1-3GlcNAc) unlike T-disaccharide, is unable to
inhibit the ABL interaction, thus showing the great importance of the
position of the axial C-4 hydroxyl group of GalNAc in T-disaccharide. This
finding could explain the inhibitory ability of Galbeta1-6GlcNAc and
lactose because C-4 and C-3 hydroxyl groups of reducing Glc, respectively,
occupy a similar position as reported by conformational analysis. From the
comparison of different glycolipids bearing terminal T-disaccharide bound
to different linkages, it can be seen than ABL binding is even more
impaired by an adjacent C-6 residual position than by the anomeric
influence of T-disaccharide. Furthermore, the addition of beta-GlcNAc to
the terminal T-disaccharide in C-3 position of Gal does not affect the ABL
binding whereas if an anionic group such as glucuronic acid is added to
C-3, the binding is partially affected. These findings demonstrate that ABL
holds a particular binding nature different from that of other
T-disaccharide specific lectins.
相似文献