974 resultados para Ecological Studies
Resumo:
A variety of nanostructures are being investigated as functional drug carriers for treatment of a wide range of diseases, most notably cardiovascular defects, autoimmune diseases, and cancer. The aim of this present contribution is to evaluate potentially applicable nanomaterials in the diagnosis and treatment of cancer due to their photophysical and photobiological properties and complexation behavior. The delivery systems consisted of chloro-aluminum phthalocyanine associated with beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin. The preparation of the complex and its stoichiometry in an ethanol/buffer (3:1) solution were studied by spectroscopic techniques, which were defined as 1:2. The inclusion complex in the nanometer scale was observed on the basis of changes to the spectroscopic properties. The singlet oxygen production and complex photophysical parameters were determined by measuring luminescence at 1270 nm and by steady state and time resolved spectroscopic, respectively. The preparation of the complex was tested and analyzed with regard to cellular damage by visible light activation. The inclusion complex showed a higher singlet oxygen quantum yield compared with other systems and other photoactive dyes. There was also a reduction in the fluorescence quantum yield compared with the results obtained for zinc phthalocyanine in organic medium. The results reported clearly that the inclusion complex chloro-aluminum phthalocyanine/cyclodextrin showed some changes in its spectroscopy properties leading to better biodistribution and biocompatibility with a potential application in photodynamic therapy, especially in the case of neoplasy. Additionally, it also has non-oncological applications as a drug delivery system.
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Two longitudinal experiments involving Merino sheep challenged with either bovine or ovine strains of Mycobacterium avium subsp. paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the interferon-gamma test, the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Infections were induced with either a bovine or ovine strain of Map in separate experiments with infections being more easily established, in terms of faecal bacterial shedding and clinical disease when the challenge inoculum was prepared from gut mucosal tissue than cultured bacteria. The patterns of response for shedding and clinical disease were similar. Cell-mediated immune responses were proportionally elevated by at least an order of magnitude in all sheep dosed with either a bovine or ovine strain of Map. Conversely, antibody responses were only elevated in a relatively small proportion of infected sheep. Neither of the clinically affected tissue challenged sheep developed an antibody response despite the presence of persistent shedding and the development and decline in cell-mediated immunity. The results indicated that for sheep the interferon-gamma test may be useful for determining if a flock has been exposed to ovine Johne's disease. (C) 2004 Elsevier B.V. All rights reserved.
Resumo:
Nanostructured drug delivery systems (NDDS), such as liposomes, represent a growing area in biomedical research. These microheterogeneous media can be used in many biological systems to provide appropriate drug levels with a specific biodistribution. The photophysical properties of a silicon derivative of tribenzonaphthoporphyrazinato (Si-tri-PcNc) incorporated into liposome were studied by steady-state techniques, time-resolved fluorescence and laser flash photolysis. All the spectroscopy measurements performed allowed us to conclude that Si-tri-PcNc in liposome is a promising NDDS for PDT The in vitro experiments with liposomal NDDS showed that the system is not cytotoxic in darkness, but exhibits a substantial phototoxicity at 1 mu M of photosensitizer concentration and 10.0 J/cm(2) of light. These conditions are sufficient to kill about 80% of the cells.
Resumo:
In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide-silicon oxide composite xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously synthesized via protonation of metavanadate species to an ""in situ"" progressive polycondensation into silica gel. The material has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene, hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent.
Resumo:
Analytical and bioanalytical methods of high-performance liquid chromatography with fluorescence detection (HPLC-FLD) were developed and validated for the determination of chloroaluminum phthalocyanine in different formulations of polymeric nanocapsules, plasma and livers of mice. Plasma and homogenized liver samples were extracted with ethyl acetate, and zinc phthalocyanine was used as internal standard. The results indicated that the methods were linear and selective for all matrices studied. Analysis of accuracy and precision showed adequate values, with variations lower than 10% in biological samples and lower than 2% in analytical samples. The recoveries were as high as 96% and 99% in the plasma and livers, respectively. The quantification limit of the analytical method was 1.12 ng/ml, and the limits of quantification of the bioanalytical method were 15 ng/ml and 75 ng/g for plasma and liver samples, respectively. The bioanalytical method developed was sensitive in the ranges of 15-100 ng/ml in plasma and 75-500 ng/g in liver samples and was applied to studies of biodistribution and pharmacokinetics of AlClPc. (C) 2011 Elsevier B.V. All rights reserved.
Resumo:
Sonogashira cross-coupling reactions involving (E)-iodo vinyl stannanes and terminal acetylenes were carried out in the presence of Pd(PPh(3))(4), Cul and several amines, affording (Z)-tributylstannyl enynes in moderate to good yields (62-91%). Utilizing the catalytic system containing Pd(PPh(3))(4) (5%), Cul (10%), and TBAOH (40% in aqueous media) as activator, better yields (72-91%) and lower reaction times were achieved. (C) 2011 Elsevier Ltd. All rights reserved.
Resumo:
Given escalating concern worldwide about the loss of biodiversity, and given biodiversity's centrality to quality of life, it is imperative that current ecological knowledge fully informs societal decision making. Over the past two decades, ecological science has undergone many significant shifts in emphasis and perspective, which have important implications for how we manage ecosystems and species. In particular, a shift has occurred from the equilibrium paradigm to one that recognizes the dynamic, non-equilibrium nature of ecosystems. Revised thinking about the spatial and temporal dynamics of ecological systems has important implications for management. Thus, it is of growing concern to ecologists and others that these recent developments have not been translated into information useful to managers and policy makers. Many conservation policies and plans are still based on equilibrium assumptions. A fundamental difficulty with integrating current ecological thinking into biodiversity policy and management planning is that field observations have yet to provide compelling evidence for many of the relationships suggested by non-equilibrium ecology. Yet despite this scientific uncertainty, management and policy decisions must still be made. This paper was motivated by the need for considered scientific debate on the significance of current ideas in theoretical ecology for biodiversity conservation. This paper aims to provide a platform for such discussion by presenting a critical synthesis of recent ecological literature that (1) identifies core issues in ecological theory, and (2) explores the implications of current ecological thinking for biodiversity conservation.
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Ficus arpazusa Casaretto is a fig tree native to the Atlantic Rain Forest sensu lato. High levels of genetic diversity and no inbreeding were observed in Ficus arpazusa. This genetic pattern is due to the action of its pollinator, Pegoscapus sp., which disperses pollen an estimated distance of 5.6 km, and of Ficus arpazusa`s mating system which, in the study area, is allogamous. This study highlights the importance of adding both ecological and genetic data into population studies, allowing a better understanding of evolutionary processes and in turn increasing the efficacy of forest management and revegetation projects, as well as species conservation.
Resumo:
Objective. To describe homicide mortality in the municipality of Sao Paulo according to type of weapon, sex, race or skin color, age, and areas of socioeconomic inequalities, between 1996 and 2008. Method. For this ecological time-series study, data about deaths in the municipality of Sao Paulo were collected from the municipal program for improvement of mortality information, using International Classification of Diseases, 10th revision (ICD-10) codes. Homicide mortality rates (HMR) were calculated for the overall population and specifically for each sex, race or skin color, age range, type of weapon, and occurrence in social deprivation/affluence areas. HMR were adjusted for age using the direct method. The percentage age of variation in HMR was calculated for the study period. For areas of socioeconomic inequalities, the relative risk of death from homicide was calculated. Results. HMR fell 73.7% between 2001 and 2008. A reduction in HMR was observed in all groups, especially males (-74.5%), young men between 15 and 24 years of age (-78.0%), and residents in areas of extreme socioeconomic deprivation (-79.3%). The reduction occurred mostly in firearm homicide rates (-74.1%). The relative risk of death from homicide in areas of extreme socioeconomic deprivation, as compared to areas with some degree of socioeconomic deprivation, was 2.77 in 1996, 3.9 in 2001, and 2.13 in 2008. In areas of high socioeconomic deprivation, the relative risk was 2.07 in 1996 and 1.96 in 2008. Conclusions. To understand the reduction in homicide rates in the municipality of Sao Paulo, it is important to take into consideration macrodeterminants that affect the entire municipality and all population subgroups, as well as micro/local determinants that have special impact on homicides committed with firearms and on subgroups such as the young, males, and residents of areas of high socioeconomic deprivation.
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The Jabirian Corpus refers to the K. Thahirat Al-`Iskandar, ""The Book of the Treasure of Alexander"" (hereafter BTA), as one of several forgeries suggesting that alchemical secrets were hidden in inscriptions in various places. The book was neglected until 1926, when Julius Ruska discussed it in his work on the Emerald Tablet, placing the BTA within the literature related to the development of Arabic alchemy. His preliminary study became an essential reference and encouraged many scholars to work on the BTA in the following decades. Some years ago, we completed the first translation of the BTA into a Western language. The work was based on the acephalous Escorial manuscript, which we identified as a fourteenth-century copy of the BTA. This manuscript is peculiar, as part of it is encoded. After finishing our translation, we started to establish the text of the BTA. At present, the text is in process of fixation-to be followed by textual criticism-and has been the main focus of a thorough study of ours on medieval hermeticism and alchemy. A sample of the work currently in progress is presented in this paper: an analysis of the variations between different manuscripts along with a study and English translation of its alchemical chapter.
Resumo:
We add to current discussions about the interface between ecology, values, and objectivity by reporting on a novel Delphi-based study of the scientific reasoning employed by a group of eight ecologists as they collectively considered current ecological thinking. We rely on contextual empiricism, with its features of multiple ways of relating theory to reality and science as a social activity, to provide a richer understanding of scientific objectivity. This understanding recognizes the place and contributions of values and, in so doing, moves the discussion beyond whether or not science is value neutral.
Resumo:
There is a widely held paradigm that mangroves are critical for sustaining production in coastal fisheries through their role as important nursery areas for fisheries species. This paradigm frequently forms the basis for important management decisions on habitat conservation and restoration of mangroves and other coastal wetlands. This paper reviews the current status of the paradigm and synthesises the information on the processes underlying these potential links. In the past, the paradigm has been supported by studies identifying correlations between the areal and linear extent of mangroves and fisheries catch. This paper goes beyond the correlative approach to develop a new framework on which future evaluations can be based. First, the review identifies what type of marine animals are using mangroves and at what life stages. These species can be categorised as estuarine residents, marine-estuarine species and marine stragglers. The marine-estuarine category includes many commercial species that use mangrove habitats as nurseries. The second stage is to determine why these species are using mangroves as nurseries. The three main proposals are that mangroves provide a refuge from predators, high levels of nutrients and shelter from physical disturbances. The recognition of the important attributes of mangrove nurseries then allows an evaluation of how changes in mangroves will affect the associated fauna. Surprisingly few studies have addressed this question. Consequently, it is difficult to predict how changes in any of these mangrove attributes would affect the faunal communities within them and, ultimately, influence the fisheries associated with them. From the information available, it seems likely that reductions in mangrove habitat complexity would reduce the biodiversity and abundance of the associated fauna, and these changes have the potential to cause cascading effects at higher trophic levels with possible consequences for fisheries. Finally, there is a discussion of the data that are currently available on mangrove distribution and fisheries catch, the limitations of these data and how best to use the data to understand mangrove-fisheries links and, ultimately, to optimise habitat and fisheries management. Examples are drawn from two relatively data-rich regions, Moreton Bay (Australia) and Western Peninsular Malaysia, to illustrate the data needs and research requirements for investigating the mangrove-fisheries paradigm. Having reliable and accurate data at appropriate spatial and temporal scales is crucial for mangrove-fisheries investigations. Recommendations are made for improvements to data collection methods that would meet these important criteria. This review provides a framework on which to base future investigations of mangrove-fisheries links, based on an understanding of the underlying processes and the need for rigorous data collection. Without this information, the understanding of the relationship between mangroves and fisheries will remain limited. Future investigations of mangrove-fisheries links must take this into account in order to have a good ecological basis and to provide better information and understanding to both fisheries and conservation managers.
Resumo:
wPrey species show specific adaptations that allow recognition, avoidance and defense against predators. For many mammalian species this includes sensitivity towards predator-derived odors. The typical sources of such odors include predator skin and fur, urine, feces and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, voles, deer, rabbits, gophers, hedgehogs, possums and sheep. Field and laboratory studies show that predator odors have distinctive behavioral effects which include (1) inhibition of activity, (2) suppression of non-defensive behaviors such as foraging, feeding and grooming, and (3) shifts to habitats or secure locations where such odors are not present. The repellent effect of predator odors in the field may sometimes be of practical use in the protection of crops and natural resources, although not all attempts at this have been successful. The failure of some studies to obtain repellent effects with predator odors may relate to (1) mismatches between the predator odors and prey species employed, (2) strain and individual differences in sensitivity to predator odors, and (3) the use of predator odors that have low efficacy. In this regard, a small number of recent studies have suggested that skin and fur-derived predator odors may have a more profound lasting effect on prey species than those derived from urine or feces. Predator odors can have powerful effects on the endocrine system including a suppression of testosterone and increased levels of stress hormones such as corticosterone and ACTH. Inhibitory effects of predator odors on reproductive behavior have been demonstrated, and these are particularly prevalent in female rodent species. Pregnant female rodents exposed to predator odors may give birth to smaller litters while exposure to predator odors during early life can hinder normal development. Recent research is starting to uncover the neural circuitry activated by predator odors, leading to hypotheses about how such activation leads to observable effects on reproduction, foraging and feeding. (c) 2005 Elsevier Ltd. All rights reserved.
Resumo:
The supplementary motor area (SMA) is thought to play in important role in the preparation and organisation of voluntary movement. It has long been known that cortical activity begins to increase up to 2 s prior to voluntary self-initiated movement. This increasing premovement activity measured in EEG is known as the Bereitschaftspotential or readiness potential. Modern functional brain imaging methods, using event-related and time-resolved functional MRI techniques, are beginning to reveal the role of the SMA, and in particular the more anterior pre-SMA, in premovement activity associated with the readiness for action. In this paper we review recent studies using event-related time-resolved fMRI methods to examine the time-course of activation changes within the SMA throughout the preparation, readiness and execution of action. These studies suggest that the preSMA plays a common role in encoding or representing actions prior to our own voluntary self-initiated movements, during motor imagery, and from the observation of others' actions. We suggest that the pre-SMA generates and encodes motor representations which are then maintained in readiness for action. (c) 2005 Elsevier B.V. All rights reserved.