Synthesis of silver nanoparticles using a modified Tollens’ method in conjunction with phytochemicals and assessment of their antimicrobial activity

Background: Silver nanoparticles (AgNPs) have attracted great attention due to their outstanding electrical, optical, magnetic, catalytic, and antimicrobial properties. However, there is a need for alternative production methods that use less toxic precursors and reduce their undesirable by-products. Phyto-extracts from the leaves of olive and rosemary plants can be used as reducing agents and (in conjunction with Tollens’ reagent) can even enhance AgNP antimicrobial activity. Methods: Conditions for the proposed hybrid synthesis method were optimized for olive leaf extracts (OLEs) and rosemary leaf extracts (RLEs). The resultant AgNPs were characterized using UV–visible spectroscopy, an environmental scanning electron microscope, and Dynamic Light Scattering analysis. An atomic absorption spectrophotometer was used to measure AgNP concentration. Fourier transform infrared spectroscopy (FTIR) was used to determine the specific functional groups responsible for the reduction of both silver nitrate and capping agents in the leaf extract. Additionally, the antimicrobial properties of the synthesized AgNPs were assessed against Gram-negative bacteria (Escherichia coli and Salmonella enterica) and Gram-positive bacteria (Staphylococcus aureus), by using both the Kirby–Bauer and broth microdilution methods on Mueller–Hinton (MH) agar plates. Results and Discussion: A simple, feasible, and rapid method has been successfully developed for silver nanoparticle synthesis by reducing Tollens’ reagent using leaf extracts from olive and rosemary plants (widely available in Jordan). Scanning electron microscopy images showed that the method produces AgNPs with a spherical shape and average core sizes of 45 ± 2 and 38 ± 3 nm for OLE and RLE, respectively. A negative zeta potential (ζ) of −43.15 ± 3.65 mV for OLE-AgNPs and −33.65 ± 2.88mV for RLE-AgNPs proved the stability of silver nanoparticles. FTIR spectra for AgNPs and leaf extracts indicated that the compounds present in the leaf extracts play an important role in the coating/capping of synthesized nanoparticles. The manufactured AgNPs exhibited an antibacterial effect against Escherichia coli and Staphylococcus aureus with minimum inhibitory concentrations (MIC) of 9.38 and 4.69 μl/ml for OLE-AgNPs and RLE-AgNPs, respectively. The MIC for Salmonella enterica were 18.75 μl/ml for both OLE-AgNPs and RLE-AgNPs. Furthermore, our results indicated that the RLE-AgNPs exhibited a stronger antibacterial effect than OLE-AgNPs against different bacteria species. These results contribute to the body of knowledge on nanoparticle production using plant-mediated synthesis and performance. They also offer insights into the potential for scaling up this production process for commercial implementation

Metabolic strategies for the degradation of the neuromodulator agmatine in mammals

Agmatine (1-amino-4-guanidinobutane), a precursor for polyamine biosynthesis, has been identified as an important neuromodulator with anticonvulsant, antineurotoxic and antidepressant actions in the brain. In this context it has emerged as an important mediator of addiction/satiety pathways associated with alcohol misuse. Consequently, the regulation of the activity of key enzymes in agmatine metabolism is an attractive strategy to combat alcoholism and related addiction disorders. Agmatine results from the decarboxylation of L-arginine in a reaction catalyzed by arginine decarboxylase (ADC), and can be converted to either guanidine butyraldehyde by diamine oxidase (DAO) or putrescine and urea by the enzyme agmatinase (AGM) or the more recently identified AGM-like protein (ALP). In rat brain, agmatine, AGM and ALP are predominantly localised in areas associated with roles in appetitive and craving (drug-reinstatement) behaviors. Thus, inhibitors of AGM or ALP are promising agents for the treatment of addictions. In this review, the properties of DAO, AGM and ALP are discussed with a view to their role in the agmatine metabolism in mammals

Ceramic Water Filter for Point-Of-Use Water Treatment in Developing Countries: Principles, Challenges and Opportunities

Drinking water source contamination poses a great threat to human health in developing countries. Point-of-use (POU) water treatment techniques, which improve drinking water quality at the household level, offer an affordable and convenient way to obtain safe drinking water and thus can reduce the outbreaks of waterborne diseases. Ceramic water filters (CWFs), fabricated from locally sourced materials and manufactured by local labor, are one of the most socially acceptable POU water treatment technologies because of their effectiveness, low-cost and ease of use. This review concisely summarizes the critical factors that influence the performance of CWFs, including (1) CWF manufacturing process (raw material selection, firing process, silver impregnation), and (2) source water quality. Then, an in-depth discussion is presented with emphasis on key research efforts to address two major challenges of conventional CWFs, including (1) simultaneous increase of filter flow rate and bacterial removal efficiency, and (2) removal of various concerning pollutants, such as viruses and metal(loid)s. To promote the application of CWFs, future research directions can focus on: (1) investigation of pore size distribution and pore structure to achieve higher flow rates and effective pathogen removal by elucidating pathogen transport in porous ceramic and adjusting manufacture parameters; and (2) exploration of new surface modification approaches with enhanced interaction between a variety of contaminants and ceramic surfaces

Diapause as escape strategy to exposure to toxicants: response of Brachionus calyciforus to arsenic

Invertebrate organisms commonly respond to environmental fluctuation by entering diapause. Production of diapause in monogonont rotifers involves a previous switch from asexual to partial sexual reproduction. Although zooplankton have been used in ecotoxicological assays, often their true vulnerability to toxicants is underestimated by not incorporating the sexual phase. We experimentally analyzed traits involved in sexual reproduction and diapause in the cyclically parthenogenetic freshwater rotifer, Brachionus calyciflorus, exposed to arsenic, a metalloid naturally found in high concentrations in desert zones, focusing on the effectiveness of diapause as an escape response in the face of an adverse condition. Addition of sublethal concentrations of arsenic modified the pattern of diapause observed in the rotifer: investment in diapause with arsenic addition peaked earlier and higher than in non-toxicant conditions, which suggests that sexual investment could be enhanced in highly stressed environmental conditions by increased responsiveness to stimulation. Nevertheless, eggs produced in large amount with arsenic, were mostly low quality, and healthy-looking eggs had lower hatching success, therefore it is unclear whether this pattern is optimum in an environment with arsenic, or if rather arsenic presence in water bodies disturbs the optimal allocation of offspring entering diapause. We observed high accumulation of arsenic in organisms exposed to constant concentration after several generations, which suggests that arsenic may be accumulated transgenerationally. The sexual phase in rotifers may be more sensitive to environmental conditions than the asexual one, therefore diapause attributes should be considered in ecotoxicological assessment because of its ecological and evolutionary implications on lakes biodiversity

Envejecimiento de la población

•Actividades básicas de la vida diaria en personas mayores y factores asociados •Asociación entre depresión y posesión de mascotas en personas mayores •Calidad de vida en adultos mayores de Santiago aplicando el instrumento WHOQOL-BREF •Calidad de vida en usuarios con enfermedad de Parkinson, demencia y sus cuidadores, comuna de Vitacura •Caracterización de egresos hospitalarios de adultos mayores en Puerto Natales (2007-2009) •Comportamiento de las patologías incluidas como GES para el adulto mayor atendido en un Cesfam •Contribución de vitaminas y minerales a las ingestas recomendadas diarias en ancianos institucionalizados de Madrid •Estado de salud oral del paciente inscrito en el Programa de Visita Domiciliaria •Evaluación del programa de discapacidad severa en Casablanca con la matriz de marco lógico •Factores asociados a satisfacción vital en una cohorte de adultos mayores de Santiago, Chile •Pauta instrumental para la identificación de riesgos para el adulto mayor autovalente, en su vivienda •Perfil farmacológico del paciente geriátrico institucionalizado y posibles consecuencias en el deterioro cognitivo •Programa de cuidados paliativos y alivio del dolor en Puerto Natales •Rehabilitación mandibular implantoprotésica: efecto en calidad de vida relacionada con salud bucal en adultos mayores •Salud bucodental en adultos mayores autovalentes de la Región de Valparaíso •Transición epidemiológica y el estudio de carga de enfermedad en Brasi

Tackling small-scale fisheries non-compliance

Sustainable wildlife trade is critical for biodiversity conservation, livelihoods, and food security. However, compliance with wildlife trade rules and regulations aimed at sustainability cannot be taken for granted. The ecological, economic, and social impacts of non-compliance with wildlife trade rules have been widely documented across diverse biomes and can be especially acute in small-scale wildlife use contexts, which usually involve poor management and limited enforcement capacity. In this DPhil, I aim to contribute to the scientific understanding of how non-compliance in small-scale wildlife use contexts can be studied and managed, through applying innovative and interdisciplinary approaches, using a small-scale fishery in Chile as a case study. Data collection for the case study took place in the common hake (Merluccius gayi gayi) small-scale fishery in Chile’s VII region. I used specialised survey techniques for assessing non-compliant behaviours, key-informant interviews, literature review, and analysed government-based datasets. I found that most of the common hake traded in the analysed region comes from non-compliant activities. I also found that fishers' motivations for non-complying are diverse, depend on the rule, and include normative (i.e., prescriptions commonly accepted in a group, supporting desirable behaviors and forbidding undesirable ones), legitimacy-based (i.e., acceptance of decision-making and its outcomes by citizens) and instrumental motivations (i.e., economic calculation of the costs and benefits of compliance). Moreover, I found that non-compliance in this fishery is highly influenced by the operation of the supply chain and market dynamics. Specifically, I found traders’ (i.e., intermediaries) incentives to trade legal or non-compliant products help describe landings and the dynamics of the fishery. These incentives can be used to predict the effect of potential interventions to reduce non-compliant use. Based on the evidence gathered, I provide policy recommendations and guidelines to reduce the extent of non-compliant behaviours in this small-scale fishery case study and beyond. Likewise, in this DPhil, I provide tools and frameworks that can be used to study non-compliance in other wildlife trade contexts and to prompt new ways of thinking about how to intervene when non-compliance in small-scale wildlife use contexts is present. These tools and frameworks can be used to compare and contrast between cases, learn from experiences, and connect researchers working in diverse social-ecological systems under a common umbrella. This research demonstrates the need to systematically tackle non-compliance in small-scale wildlife use contexts, considering the diversity of actors involved and their motivations, and the market and supply chain used to trade wildlife products.</p

Mar, costas y pesquerías: una mirada comparativa desde Chile, México y Perú

El objetivo de esta publicación es doble: por un lado, responder a una necesidad y vacío en la reflexión y análisis de temas institucionales, políticos y normativos sobre mares, océanos, áreas costeras y pesquerías en Perú, México y Chile; en segundo lugar, busca aportar a la discusión política y agendas nacionales en un contexto de crecientes oportunidades de colaboración y financiamiento internacional. La publicación contiene doce ensayos preparados por reconocidos expertos que describen y reflexionan sobre una diversidad de temas relevantes para Chile, México y Perú, pero igualmente pertinentes para otros países de América Latina y más allá. Se trata de una compilación de ensayos con estructuras comunes que ofrecen también conclusiones y recomendaciones sobre cómo avanzar y mejorar en los esfuerzos por conservar y desarrollar sosteniblemente los mares, océanos, áreas costeras y pesquerías

A framework for assessing and intervening in markets driving unsustainable wildlife use

Understanding how markets drive unsustainable wildlife use is key for biodiversity conservation. Yet most approaches to date look at isolated components of wildlife markets, hindering our ability to intervene effectively to improve sustainability. To better assess and intervene in wildlife markets, we propose a framework that integrates three analytical levels. The first level, “actor”, assesses the underlying motivations and mechanisms that allow or constrain how actors benefit from wildlife markets. The second level, “inter-actor”, assesses the configuration of wildlife product supply-chains and the type of competition between actors participating in wildlife markets. The third level, “market”, evaluates supply-demand dynamics, quantity and price determinants, and the presence and effect of illegal products flowing into markets. We showcase the utility of the framework in a data-limited small-scale fishery case study (common hake, Merluccius gayi gayi in Chile); our mixed-method analysis provided relevant, tailored management recommendations for improving sustainability. Tackling markets driving unsustainable wildlife use needs integrated approaches that bring together the diversity of factors affecting wildlife market dynamics

Motivations for (non-) compliance with conservation rules by small-scale resource users

Understanding compliance with conservation rules is key for biodiversity conservation. Here, we assess compliance and its underlying motivations in a small-scale fishery in Chile. We adapt a framework originally developed for forestry to unpack compliance motivations at within-individual and between-individuals levels while accounting for contextual factors. We find that 92-100% fishers comply with temporal or gear rules, while only 3% comply with the quota limit. Legitimacy-based motivations are more important in explaining why individual fishers comply with temporal/gear rules than they are for compliance with the quota. At the between-individuals level, we find that normative motivations are significantly related to the degree of non-compliance with the quota. Contextual factors such as quota levels are key in explaining broader non-compliance patterns. Our results suggest that considering compliance at appropriate analytical levels is necessary to unpack motivations, guide local and national natural resource management policies, and move towards a better theory of compliance

A synthesis of (non‐)compliance theories with applications to small‐scale fisheries research and practice

Non‐compliance in fisheries is a persistent challenge for the conservation and sustainable management of the oceans and has particularly acute impacts in small‐scale fisheries contexts. Small‐scale fisheries often suffer from chronic overexploitation, poor management, lack of enforcement and non‐compliance, but small‐scale fishers are highly dependent on the ocean as a source of employment and food. Improving our understanding of the determinants of non‐compliant behaviours in small‐scale fisheries can help develop strategies to prevent and reduce its consequences. Here, we review two main approaches for the study of non‐compliant behaviours and crimes more broadly, spanning criminology, economics and psychology. On the one hand, actor‐based approaches address the underlying motivations for people to comply or not with regulations. Opportunity‐based approaches, on the other hand, assume that non‐compliance is not distributed randomly across space and time and focuses on the role that the immediate environment plays in the performance of non‐compliant behaviours. We discuss potential applications of actor‐based and opportunity‐based approaches in guiding small‐scale fisheries non‐compliance research. Moreover, we provide guiding principles for integrating these approaches in a complementary way, highlighting opportunities and challenges for building a better non‐compliance research agenda for fisheries and beyond. Addressing non‐compliance is a common challenge for natural resource management in multiple ecosystems. Integrating these two perspectives has the potential to improve both research and practice