Superparamagnetic Poly (3-hydroxybutyrate-co-3 hydroxyvalerate) (PHBV) nanoparticles for biomedical applications

Indexación: ScieloBackground: The progress in material science and the recent advances in biodegradable/biocompatible polymers and magnetic iron oxide nanoparticles have led to develop innovative diagnostic and therapeutic strategies for diseases based on multifunctional nanoparticles, which include contrast medium for magnetic resonance imaging, agent for hyperthermia and nanocarriers for targeted drug delivery. The aim of this work is to synthesize and characterize superparamagnetic iron oxide (magnetite), and to encapsulate them into poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles for biomedical applications. Results: The magnetite nanoparticles were confirmed by X-ray diffraction and exhibited a size of 22.3 ± 8.8 nm measured by transmission electron microscopy (TEM). Polymeric PHBV nanoparticles loaded with magnetite (MgNPs) were analyzed using dynamic light scattering and showed a size of 258.6 ± 35.7 nm and a negative zeta potential (-10.8 ± 3.5 mV). The TEM examination of MgNPs exhibited a spherical core-shell structure and the magnetic measurements showed in both, non-encapsulated magnetite and MgNPs, a superparamagnetic performance. Finally, the in vitro studies about the magnetic retention of MgNPs in a segment of small intestine of rats showed an active accumulation in the region of the magnetic field. Conclusions: The results obtained make the MgNPs suitable as potential magnetic resonance imaging contrast agents, also promoting hyperthermia and even as potential nanocarriers for site-specific transport and delivery of drugs. Keywords: hyperthermia, magnetic resonance image (MRI), magnetite, PHBV, polymeric nanoparticles.http://ref.scielo.org/cxt57

Accessible areas in ecological niche comparisons of invasive species: Recognized but still overlooked

Understanding biological invasions is crucial for their control and prevention. Specially, establishing whether invasive species operate within the constraint of conservative ecological niches, or if niche shifts occur at all commonly as part of the invasion process, is indispensable to identifying and anticipating potential areas of invasion. Ecological niche modeling (ENM) has been used to address such questions, but improvements and debate in study design, model evaluation, and methods are still needed to mature this field. We reanalyze data for Gray Squirrels (Sciurus carolinensis), native to North America, but invasive in Europe. Our main finding was that, when the analysis extent is established carefully based on analogous sets of environmental conditions, all evidence of niche shifts disappears, suggesting that previous reports of niche shifts for this species are artifacts of methods and interpretation, rather than biological reality. Niche conservatism should be tested only within appropriate, similar, environmental spaces that are accessible to both species or populations being compared, thus avoiding model extrapolation related to model transfers. Testing for environmental similarity between native and invaded areas is critical to identifying niche shifts during species invasion robustly, but also in applications of ENM to understanding temporal dimensions of niche dynamics

Zika Virus, Elevation, and Transmission Risk

Introduction: Zika virus has appeared in the Americas in the form of a major outbreak, and is now known to cause birth defects when pregnant women are infected. As a result, the Centers for Disease Control and Prevention issued travel guidelines, in the form of an elevational risk definition: destinations below 2000m are considered as at-risk. Methods: We explored the distribution of known Zika virus vector mosquito species in relation to climatic conditions, elevation, latitude, and air traffic connections to the United States. Results: In view of the tropical and subtropical nature of the mosquito species that are the primary Zika virus vectors, we point out that climate varies rather dramatically with respect to elevation and latitude, such that a single elevational criterion will be a poor predictor of potential for transmission. Discussion: We suggest an initial adjustment would consider latitude in addition to elevation; a more definitive, quantitative analysis of risk would consider variables of ecology, climate, human condition, and connectivity of areas

On the existence of initial data containing isolated black holes

We present a general construction of initial data for Einstein's equations containing an arbitrary number of black holes, each of which is instantaneously in equilibrium. Each black hole is taken to be a marginally trapped surface and plays the role of the inner boundary of the Cauchy surface. The black hole is taken to be instantaneously isolated if its outgoing null rays are shear-free. Starting from the choice of a conformal metric and the freely specifiable part of the extrinsic curvature in the bulk, we give a prescription for choosing the shape of the inner boundaries and the boundary conditions that must be imposed there. We show rigorously that with these choices, the resulting non-linear elliptic system always admits solutions.Comment: 11 pages, 2 figures, RevTeX

Carnivore-Livestock Conflicts in Chile: Evidence and Methods for Mitigation

Human population growth and habitat loss have exacerbated human–wildlife conflicts worldwide. We explored trends in human–wildlife conflicts (HWCs) in Chile using scientific and official reports to identify areas and species with higher risk of conflicts and tools available for their prevention and mitigation. The puma (Puma concolor) was considered the most frequent predator; however, fox (Lycalopex spp.) and free-ranging or feral dog (Canis lupus familiaris) attacks were also common. Our results suggest that the magnitude of puma conflicts may be overestimated. Domestic sheep (Ovis spp.) and poultry (Galliformes) were the most common species predated. Livestock losses were widespread across Chile but were highest in San Jose de Maipo, located in central Chile, and Cochrane, La Unión, and Lago Verde in south Chile municipalities. Livestock guardian dogs and the livestock insurance, as a part of the Agriculture Insurance of Chile, were identified as the most promising tools to mitigate HWCs, short- and mid-term, respectively. However, longer-term strategies should focus on improving livestock management through extension (i.e., farmer education) programs for local communities. In Chile, HWCs negatively impact small farmers and wild carnivore populations. An interinstitutional and interdisciplinary strategy integrating input from government and nongovernmental organizations, farmers, and academia is needed to achieve effective carnivore conservation in the long-term

Macroinvertebrados bentónicos de dos lagos tropicales de alta montaña en el volcán Nevado de Toluca, en la región central de México

The benthic macroinvertebrates play an important role in the organic matter recycling and are sensitive indicators of human perturbation. Goals. The aim of this study was to recognize the spatial and temporal variation in taxonomic richness and density of the benthic macroinvertebrates of high mountain Lakes El Sol and La Luna, and their relationship with the environmental variables. Methods. Three deep stations (El Sol = 2 and La Luna = 1) and two in the littoral zone of El Sol (with and without vegetation) were selected. Results. We found eight taxa in El Sol: four oligochaetes (Limnodrilus hoffmeisteri, Tubifex tubifex, Lumbriculus variegatus and Nais pardalis), one bivalve (Pisidium casertanum), one hydrozoan (Hydra vulgaris) and two chironomids (Pagastia sp. and Tanytarsus sp.). Differently in La Luna there were just L. hoffmeisteri y Pagastia sp. The average density of the benthic macroinvertebrates was similar in the deep zone of both lakes (El Sol 5,526 ± 3,807 org m-2 y La Luna 7,955 ± 7,349 org m-2). The density in the shallow zone without vegetation was higher (38,249 ± 33.077 org m-2) than in the vegetated shallow zone (25.247 ± 18.997 org m-2). Conclusions. The temporal variation of macroinvertebrates density seems to be regulated by the temperature and pH, showing the lowest values when the temperature and pH are lower.Los macroinvertebrados bentónicos son importantes debido a su papel en la remineralización de la materia orgánica y como indicadores por ser sensibles a las perturbaciones derivadas de las actividades humanas. Objetivos. Analizar la distribución espacial y temporal de la riqueza taxonómica y la densidad de los macroinvertebrados bentónicos y su relación con algunas las variables ambientales en dos lagos tropicales de alta montaña localizados en el volcán Nevado de Toluca, en el centro de México. Métodos. Se seleccionaron dos estaciones profundas y dos someras (con y sin vegetación) para el lago de El Sol y una estación profunda para La Luna. Resultados. En El Sol se identificaron cuatro especies de oligoquetos (Limnodrilus hoffmeisteri, Tubifex tubifex, Lumbriculus variegatus y Nais pardalis), un bivalvo (Pisidium casertanum), un hidrozoario (Hydra vulgaris) y dos quironómidos (Pagastia sp. y Tanytarsus sp.). En La Luna solo se encontró a L. hoffmeisteri y Pagastia sp. Las densidades promedio de los macroinvertebrados bentónicos en la zona profunda de ambos lagos fueron similares (El Sol 5,526 ± 3,807 org m-2 y La Luna 7,955 ± 7,349 org m-2). La densidad en la zona somera sin vegetación en El Sol fue de 38,249 ± 33,077 org m-2, mientras que en la estación con vegetación la densidad fue de 25,247 ± 18,997 org m-2. Conclusiones. La variación temporal de la densidad de los macroinvertebrados parece estar regulada por la temperatura y el pH, presentándose los menores valores cuando la temperatura y el pH son más bajos

Acoplamiento pelágico-bentónico: respuesta de la zona bentónica profunda a la sedimentación del florecimiento invernal de diatomeas en el lago oligotrófico Alchichica, Puebla, México

The aim of this study is to recognize the existence of a pelagic-benthic coupling in the oligotrophic, tropical Lake Alchichica through analysis of the response of the deep benthic zone to the winter diatom bloom deposition. The water column phytoplankton biomass and the sedimentary chlorophyll a were analyzed along an annual cycle. Alchichica is a warm monomictic lake circulating in winter and stratified over the rest of the year. The presence of turbulence and nutrient availability during the mixing period, favor the development of a diatom bloom composed by large species (e. g., Cyclotella alchichicana) which are not totally consumed and settle down. The deep benthic zone responds to the sinking of the winter diatom bloom with the prompt development and permanence for an extended period- of hypolimnetic anoxia, which in turns prevents the establishment and development of the benthic fauna in Lake Alchichica, and favors the internal loss of nitrogen through denitrification, and accordingly, promotes nitrogen to be the limiting nutrient for phytoplankton growth.El objetivo del presente estudio es reconocer la existencia de un acoplamiento pelágico-bentónico en el lago oligotrófico tropical Alchichica evaluando la respuesta de la zona bentónica profunda a la sedimentación del florecimiento invernal de diatomeas. Se midió la biomasa fitoplanctónica en la columna de agua a lo largo de un ciclo anual, al igual que la concentración de clorofila a sedimentaria. Alchichica es un lago monomíctico cálido con un periodo de circulación invernal y estratificación el resto del año. La presencia de turbulencia y nutrimentos durante el periodo de circulación favorecen el desarrollo de un florecimiento de diatomeas compuesto por especies de talla grande (p. e., Cyclotella alchichicana), las cuales se sedimentan al no ser consumidas en su totalidad. La zona bentónica profunda del lago responde a la sedimentación del florecimiento invernal de diatomeas con el desarrollo y permanencia por un periodo prolongado de anoxia hipolimnética, lo que a su vez, impide el establecimiento y desarrollo de fauna bentónica en el Lago Alchichica, favorece la pérdida interna de nitrógeno por desnitrificación y consecuentemente, conlleva a que el nitrógeno sea el elemento que más frecuentemente límite el crecimiento fitoplanctónico

Tracking infectious diseases in a warming world.

Using infectious diseases sensitive to climate as indicators of climate change helps stimulate andinform public health response