1,436 research outputs found
Assessment of potential mare stocking impacts on resource access rights and livelihoods in Komio village, Niger River Delta, Mali
The Community-based Fish Culture in Seasonal Floodplains and Irrigation Systems (CBFC) project is a five year research project supported by the Challenge Program on Water and Food (CPWF), with the aim of increasing productivity of seasonally occurring water bodies through aquaculture. The project has been implemented in Bangladesh, Cambodia, China, Mali and Vietnam, where technical and institutional options for community based aquaculture have been tested. The project began in 2005 and was completed in March 2010. In the context of the CP-35 project, this visit follows up on a preliminary assessment of livelihoods and institutions in Komio village, Mali conducted by consultants Joffre and Lajaunie. The objective of the visit was to determine how stocking mares around Komio village may impact livelihoods and access rights to aquatic resources. Additional insights were gained from the governance experiences and livelihood impacts of village irrigation schemes (PIVs).Fishing rights, River fisheries, Livelihoods
Development and Evaluation Of HIV gp120 Responsive Microbicide Formulation for the Prevention of HIV Sexual Transmission
Sexual transmission of HIV remains the primary route (75 to 85%) of HIV infection among
all new infection cases. Furthermore, women represent the most vulnerable population and are
more susceptible to HIV infections than their male counterpart. Thus, there is an urgent need to
develop topical (vaginal/rectal) microbicide formulations capable of preventing HIV sexual
transmission. The objective of this dissertation is to develop a mannose specific, lectin-based
topical microbicide formulation capable of targeting HIV gp120 for the prevention of HIV sexual
transmission. In Chapters 1 and 2, the general hypothesis, aims and scope of this work are
introduced. Chapter 3 covers the literature review of anti-HIV lectins and current delivery
approaches.
In Chapter 4, the binding interactions between the mannose specific lectin Concanavalin
A (ConA) and glycogen from Oster, as well as mannan from Saccharomyces cerevisiae, were
studied using a quartz crystal microbalance (QCM). The equilibrium dissociation constant
describing the interaction between Con A and glycogen (KD = 0.25 μM) was 12 fold lower than
the equilibrium dissociation constant describing the binding between Con A and mannan (KD =
2.89 μM). That is, Con A was found to have a higher affinity for the glucose-base polysaccharide,
than for the mannose-based. This observation was mainly attributed to steric effects, the difference
in molecular weight and branching pattern of both polysaccharides.
The knowledge gained in Chapter 4 was applied in Chapter 5 for the development of HIV
1 gp120 and mannose responsive particle (MRP) formulations. Thus, core dissolved MRP
(−) and core containing MRP (+) were prepared through the layer-by-layer coating
of calcium carbonate (CaCO3) with the mannose specific lectin (Con A) and a polysaccharide
cross-linker (Glycogen). Particles were characterized and tested in vitro on Lactobacillus
crispatus, Human vaginal keratinocytes (VK2/E6E7) and murine macrophage [RAW 264.7 (TIB
71)] cell lines. + average size and ζ-potential were 1130±15.72 nm [PDI = 0.153] and
15.1±0.55 mV, (n=3). Similarly, − average size and ζ-potential were 1089±23.33 nm (n=3)
and -14.2±0.25 mV (n=3). Tenofovir (TFV) encapsulation efficiency in CaCO3 was 74.4% with
drug loading of 16.3% w/w and 6.0% w/w in + and −, respectively. Both −
and + were nontoxic to L. crispatus and did not induce any significant pro-inflammatory
nitric oxide release in VK2 and RAW 264.7 cell culture. However, − was found to
significantly affect VK2 and RAW 264.7 cells viability at concentrations ≥ 100 µg/ml. Similarly,
− significantly increased pro-inflammatory cytokines (IL1α, IL1β, IL6, IL7, MKC and
TNFα) release at concentrations ≥ 100 µg/ml. Conversely, + did not induce any significant
changes in VK2 and RAW 264.7 cells viability nor in pro-inflammatory cytokines’ levels, in the
concentration range tested (≤ 1000 µg/ml), for 24 h. + was then selected for further in vitro
drug release studies as well as ex vivo vaginal mucoadhesion studies. HIV gp120 triggered TFV
release from + in a concentration dependent manner, and following Hixson–Crowell and
Hopfenberg kinetic models, consistent with drug release from diminishing surface or matrix
eroding drug particles. + was further optimized by varying the number of Con A layer in
the formulation, and in order to achieve lower HIV gp120 sensitivity (≤ 100 µg/ml). Furthermore,
bioadhesion studies, performed ex vivo on porcine vaginal tissue, demonstrated that
FITC−+ adheres to vaginal tissue at levels varying between 10% ± 1 and 20% ± 2,
depending on the number of Con A layers in the formulation.
In chapter 6, + preclinical safety was evaluated in 8-12 weeks old female C57BL/6
mice model. First, mice were treated with Depo-Provera® to maintain them in a diestrus-like state.
Then the microbicide formulation was delivered vaginally at a dose of 100 mg/kg in PBS. Vaginal
histology, immunohistochemistry evaluations, as well as pro-inflammatory cytokines release
(vaginal lavage and tissue extract) were investigated after 24 h. The vaginal retention of
FITC−+ was also evaluated, up to 24 h. Vaginal and major reproductive organs’ histology
did not show major damage of the epithelial layer. This result was also consistent with
immunohistochemistry evaluation of CD45+ cells infiltration in the vaginal epithelial layer, unlike
the positive control treated groups (BZK and N-9). Furthermore + did not induce any
significant changes in pro-inflammatory cytokines IL1α, Ilβ, IL7, IP10 and TNFα. In addition, it
was also observed that FITC labeled + does not have a long-term retention in mice vaginal
tract. This result suggested that a precoital or multiple vaginal application (i.e., BID) approaches
of + should be investigated.
Overall, this study demonstrates the feasibility of lectin-based microbicide formulations to
target HIV gp120 for the prevention of HIV sexual transmission
Farmers’ Perceptions and Willingness to Pay for Metarhizium-based Biopesticide to Control Cotton Bollworms in Benin (West Africa)
The study assesses farmers’ perceptions and willingness to pay for a biopesticide developed from Metarhizium anisopliae a fungi. A sample of 400 conventional and organic cotton producers was randomly selected in cotton producing zones in Benin and interviewed for their perceptions on the efficacy of the biopesticide and the likely prices they are willing to pay for the product to control a major pest like Helicoverpa armigera or cotton bollworm causing substantial crop losses. An econometric model (Logit) is used to identify factors highly likely to affect farmer’s willingness to purchase the product. The results show that Helicoverpa armigera or cotton bollworm is perceived by farmers as the most severe pest with losses reaching up to 100%. Farmers attribute the current pest intensity to a number of factors including ineffectiveness of chemical pesticides, delay in access to input mainly fertilizers and the development of refuge host plants for cotton pests. The results also show that most cotton producers and their households members are exposed to chemical insecticides without adequate protection devices during the pest control sprays. Both organic and conventional cotton producers have expressed a significant interest in the use of Metarhizium to control Helicoverpa on cotton. Both types of farmers willing to pay more for any pest control product that would improve cotton product quality for higher cotton price. Three variables influencing farmers’ willing to pay for biopesticides from Metarhizium were efficacy, agro-ecological zone and broad spectrum.Biopesticides, Cotton bollworms, farmers survey, Benin, Agricultural and Food Policy, Community/Rural/Urban Development, Demand and Price Analysis, Farm Management, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Relations/Trade, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,
Impact Assessment of agricultural research and development to reduce virus problems in tomato production in Mali: Farmers perceptions
Pests and diseases caused by bacteria, nematodes, fungi and viruses cause significant losses to tomato in West Africa. This study, carried-out within the framework of the IPM-CRSP implemented jointly by IITA, IER and Virginia Tech. and State University, assesses farmers’ perceptions on tomato pests and analyzes factors affecting pest management decision-making. Surveys were carried out in three tomato production areas where pests and diseases are major agricultural problems encountered by farmers. Data were collected a sample of from 343 farmers through a set of questionnaires on tomato production systems. Farmer’s decision-making in pest management was modeled using an econometrics Logit probability model. Results show that the main disease reported by most farmers is tomato leaf curl viruses transmitted by whitefly (Bemissia tabaci). The spray of chemicals was not effective on whitefly-transmitted viruses, but the observance of host free period could significantly reduce the population of whiteflies. Key factors affecting farmers’ pest management decision-making are gender; share of tomato income from household income and the level of farm income. Men are more involved in tomato production due to access to pesticide and effective demand for pesticides because of incomes (purchasing power). This paper concludes that tomato production can increase significantly if improved varieties tolerant to whitefly viruses are developed and disseminated, and farmers trained on the appropriate use of chemicals using a participatory approach to raise their level of awareness and information on effective pesticide use and pest-management decision-making.Agricultural and Food Policy, Agricultural Finance, Crop Production/Industries, Demand and Price Analysis, Environmental Economics and Policy, Farm Management, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Relations/Trade, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,
Institutional histories, seasonal floodplains (mares), and livelihood impacts of fish stocking in the Inner Niger River Delta of Mali
The Community-based Fish Culture in Seasonal Floodplains and Irrigation Systems (CBFC) project is a five year research project supported by the Challenge Program on Water and Food (CPWF), with the aim of increasing productivity of seasonally occurring water bodies through aquaculture. The project has been implemented in Bangladesh, Cambodia, China, Mali and Vietnam, where technical and institutional options for community based aquaculture have been tested. The project began in 2005 and was completed in March 2010. The seasonally flooded depressions in the Inner Niger Delta (known as mares) represent a critical fishery resource for the inhabitants of the village of Komio, and at present, access is open to all residents. A proposal to build stocked fish enclosures in the main village mare presents potential benefits and risks. On one hand, overall productivity in the mare could be significantly increased, providing important sources of protein and cash during the annual drought period, when few livelihood activities can be performed and when village livelihoods are at their most vulnerable. Enhanced productivity in mares may also decrease local household pressures for seasonal labor migration. On the other hand, a resulting increase in the value of these mares may encourage elite capture of project benefits or rentseeking by certain village leaders of the landowning Marka ethnic group. Using qualitative interviews and focus group discussions, the study provides evidence of how local institutional and leadership capacity for equitable common property resource management have evolved since the introduction of irrigated farming systems (known as PΘrimΦtres IrriguΘs Villageois or PIVs) in the 1990s.Fishing rights, River fisheries, Livelihoods
Efficacy and safety of praziquantel in preschool-aged children in an area co-endemic for Schistosoma mansoni and S. haematobium
BACKGROUND: In sub-Saharan Africa the recommended strategy to control schistosomiasis is preventive chemotherapy. Emphasis is placed on school-aged children, but in high endemicity areas, preschool-aged children are also at risk, and hence might need treatment with praziquantel. Since a pediatric formulation (e.g., syrup) is not available outside of Egypt, crushed praziquantel tablets are used, but the efficacy and safety of this treatment regimen is insufficiently studied.METHODOLOGY: We assessed the efficacy and safety of crushed praziquantel tablets among preschool-aged children (>6 years) in the Azaguié district, south Côte d'Ivoire, where Schistosoma mansoni and S. haematobium coexist. Using a cross-sectional design, children provided two stool and two urine samples before and 3 weeks after treatment. Crushed praziquantel tablets, mixed with water, were administered at a dose of 40 mg/kg. Adverse events were assessed and graded 4 and 24 hours posttreatment by interviewing mothers/guardians.PRINCIPAL FINDINGS: Overall, 160 preschool-aged children had at least one stool and one urine sample examined with duplicate Kato-Katz thick smears and a point-of-care circulating cathodic antigen (POC-CCA) cassette for S. mansoni, and urine filtration for S. haematobium diagnosis before and 3 weeks after praziquantel administration. According to the Kato-Katz and urine filtration results, we found high efficacy against S. mansoni (cure rate (CR), 88.6%; egg reduction rate (ERR), 96.7%) and S. haematobium (CR, 88.9%; ERR, 98.0%). POC-CCA revealed considerably lower efficacy against S. mansoni (CR, 53.8%). Treatment was generally well tolerated, but moderately severe adverse events (i.e., body and face inflammation), were observed in four Schistosoma egg-negative children. CONCLUSIONS/SIGNIFICANCE: Crushed praziquantel administered to preschool-aged children at a dose of 40 mg/kg is efficacious against S. mansoni and S. haematobium in a co-endemic setting of Côte d'Ivoire. Further research is required with highly sensitive diagnostic tools and safety must be investigated in more depth.TRIAL REGISTRATION: Controlled-Trials.com ISRCTN53172722
Spatiotemporal chaos induces extreme events in an extended microcavity laser
Extreme events such as rogue wave in optics and fluids are often associated
with the merging dynamics of coherent structures. We present experimental and
numerical results on the physics of extreme events appearance in a spatially
extended semiconductor microcavity laser with intracavity saturable absorber.
This system can display deterministic irregular dynamics only thanks to spatial
coupling through diffraction of light. We have identified parameter regions
where extreme events are encountered and established the origin of this
dynamics in the emergence of deterministic spatiotemporal chaos, through the
correspondence between the proportion of extreme events and the dimension of
the strange attractor
Evaluation de l’effet repulsif d’extraits de neem (Azadirachta indica A. Juss., 1830) sur le charançon de la patate douce (Cylas puncticollis Boheman, 1833) en condition de laboratoire a Korhogo, nord de la Cote d’Ivoire
Une stratégie de gestion intégrée des insectes nuisibles à la culture de la patate douce a été élaborée pour réduire les pertes dues à ceux-ci. Ainsi, les propriétés répulsives des extraits de feuilles et d’amandes de neem ont été évaluées sur Cylas puncticollis, un charançon de la patate douce. Pour ce faire, quatre concentrations d’extraits ont été préparées à raison de quatre répétitions par concentration. Le test a consisté à la détermination du pourcentage de charançons présents dans la zone traitée. Chacune des concentrations d’extraits a été appliquée sur la moitié d’un papier buvard placé dans une boite de Pétri de 9 cm de diamètre et sur lequel 10 charançons ont été posés. Les effets répulsifs des extraits ont été comparés à ceux d’un insecticide chimique et l’eau distillée. Le test avec 20 cL/L d’extraits de feuilles a causé 85 % de répulsion contre 45 % pour les amandes à 25 g/L. Les extraits ont significativement causé plus de répulsion que l’eau distillée et l’insecticide chimique. Les tests ont révélé un potentiel plus répulsif des extraits de feuilles comparé à celui des amandes. Les extraits de neem pourraient constituer une alternative crédible à la lutte chimique pour la protection de la patate douce contre ce charançon.
English title: Evaluation of the repellent effect of neem extracts (Azadirachta indica A. Juss., 1830) on the sweet potato weevil (Cylas puncticollis Boheman, 1833) under laboratory conditions in Korhogo, northern Côte d’Ivoire
Abstract
An integrated pest management strategy for sweet potatoes has been developed to reduce pest losses. Thus, the repellent properties of neem leaf and kernel extracts were evaluated on Cylas puncticollis, a sweet potato weevil. For this purpose, four concentrations of extracts were prepared with four replicates per concentration. The test consisted of determining the percentage of weevils in the treated area. Each of the extract concentrations was applied to half of a blotting paper placed in 9 cm diameter Petri dishes on which 10 weevils were placed. The repellent effects of the extracts were compared to those of a chemical insecticide and distilled water. Test with 20 cL/L leaf extract caused 85% repellence compared to 45% for almonds at 25 g/L. Compared to the chemical insecticide and distilled water, the extracts caused significantly more repellence. The tests revealed a higher repellent potential of the leaf extracts compared to those of almonds. Neem extracts could be a credible alternative to chemical control for the protection of sweet potato against this weevil.
Keywords: Neem extracts, Repellent effect, Sweet potato, Cylas puncticolli
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