Agricultural extension - generic challenges and the ingredients for solutions

Is agricultural extension in developing countries up to the task of providing the information, ideas, and organization needed to meet food needs? What role should governments play in implementing or facilitating extension services? Roughly 80 percent of the world's extension is publicly funded and delivered by civil servants, providing a range of services to the farming population, commercial producers, and disadvantaged target groups. Budgetary constraints and concerns about performance create pressure to show the payoff on investment in extension and to explore alternatives to publicly providing it. The authors analyze the challenges facing policymakers who must decide what role governments should play in implementing or facilitating extension services. Focusing on developing country experience, they identify generic challenges that make it difficult to organize extension: a) The magnitude of the task. b) Dependence on wider policy and other agency functions. c) Problems in identifying the cause and effect needed to enable accountability and to get political support and funding. d) Liability for public service functions beyond the transfer of agricultural knowledge and information. e) Fiscal sustainability. f) Inadequate interaction with knowledge generators. The authors show how various extension approaches were developed in attempts to overcome the challenges of extension: 1) Improving extension management. 2) Decentralizing. 3) Focusing on single commodities. 4) Providing free-for-service public extension services. 5) Establishing institutional pluralism. 6) Empowering people by using participatory approaches. 7) Using appropriate media. Each of the approaches has weaknesses and strengths, and in their analysis the authors identify the ingredients that show promise. Rural people know when something is relevant and effective. The aspects of agricultural extension services that tend to be inherently low cost and build reciprocal, mutually trusting relationships are those most likely to produce commitment, accountability, political support, fiscal sustainability, and the kinds of effective interaction that generate knowledge.ICT Policy and Strategies,Decentralization,Enterprise Development&Reform,Agricultural Knowledge&Information Systems,Agricultural Research,Environmental Economics&Policies,Health Monitoring&Evaluation,Agricultural Knowledge&Information Systems,ICT Policy and Strategies,Agricultural Research

De nationale Werkgroep Grondwater 2009. En een vooruitblik naar 2010

In rapport staat onderaan de pagina's een foute vermelding: "RIVM Rapport 60762600130014"De nationale Werkgroep Grondwater gaat in 2010 meer verbanden leggen tussen beleidsvelden waarin kennis- of beleidsvragen over grondwater spelen. De werkgroep richt zich sinds 2003 op een goede implementatie van het grondwatergedeelte van de Europese Kaderrichtlijn Water (KRW). In 2010 wil zij zich meer dan voorheen gaan richten op relaties tussen de KRW-implementatie en ontwikkelingen in beleidsvelden zoals Natura2000, het Deltaplan en het Convenant Bodem. Hierbij spelen niet alleen kennisvragen maar juist ook beleidsvragen en vragen van meer strategische aard. Dit briefrapport geeft een overzicht van de werkzaamheden van de nationale Werkgroep Grondwater in 2009 en biedt een vooruitblik van haar werkzaamheden in 2010 en verder. In deze werkgroep werken de ministeries, provincies, waterschappen, gemeente en onderzoeksinstituten samen aan de implementatie van het grondwatergedeelte van de Kaderrichtlijn Water en de Grondwater Dochterrichtlijn. Dit overzicht kan dienen als naslagwerk voor diegenen die in 2009 betrokken zijn geweest bij de Werkgroep Grondwater en als introductie voor diegenen die in 2010 aan de slag gaan met activiteiten die aan de onderwerpen van de werkgroep raken.VRO

The rise of new classical economics

vrije Universiteit amsterda

Study of methods for platelet function testing in the perspective of lab-on-chip applications

Research goals Platelets are reactive cells with the main function to maintain blood vessel integrity. Altered platelet function can lead to cardiovascular diseases such as thrombosis or bleeding disorders and platelets can also play a role in atherosclerosis. Current methods to quantify platelet function are laboratory techniques such as flow cytometry, aggregometry or luminescent assays. However, these techniques are complex and time consuming. Therefore we are interested in novel methods suited for future application in a lab-on-a-chip format. In our research we have focused on the use of well-established biomarkers, such as membrane marker expression, cytosolic calcium signaling and secretion markers, to quantify platelet activation as well as responsiveness. We report studies on platelet function using these read-out parameters and we discuss the relevance of the results for lab-on-a-chip biosensor research. Measurement of platelet membrane markers using antibody coated magnetic beads Magnetic beads are convenient carriers for rapid capture and manipulation of biological cells in a miniaturized system. We have studied the use of antibody coated magnetic beads to measure platelet function via membrane markers expressed upon activation. We used anti-P-selectin coated beads to capture activated platelets from samples stimulated with Thrombin Receptor Activator Peptide (TRAP). The responsiveness of the platelets was analyzed via the remaining unbound platelets in solution and compared to a reference method in which the number of activated platelets is analyzed via fluorescent labeling. The effective concentration for platelet responsiveness found with the bead capture assay (17.9 ± 4.9 µM) was in good agreement with the effective concentration found with the reference assay (23.5 ± 0.4 µM) in buffer. In 10% plasma the effective concentrations were 14.0 ± 4.4 µM and 13.8 ± 0.3 µM respectively, proving that platelet responsiveness can be quantified using antibody coated magnetic beads. In addition, we showed that we were able to discriminate between non-specific and specific interactions between functionalized beads and immobilized platelet with the use of magnetic actuation. The demonstrated read-out method is an interesting first step toward a lab-on-a-chip system for platelet function testing. Measurement of calcium signaling to study platelet-surface interactions Most lab-on-chip biosensor concepts are based on the use of a substrate for immobilization and subsequent detection of the biological system of interest. So for lab-on-chip platelet function testing it is important to understand the influence that a substrate can have on the platelets. We studied the interaction between platelets and various surfaces with calcium signaling in platelets. We used a calcium indicator and studied the response of individual platelets upon adhesion to Bovine Serum Albumin (BSA), Poly-L-lysine (PLL), mouse immunoglobulin (IgG), anti-GPIb and collagen coated surfaces. We recorded the fraction of cells that increase their cytosolic calcium upon binding to these surfaces. Furthermore, we recorded the delay time between the moments of platelet adhesion or chemical stimulation and the increase of cytosolic calcium. The experiments showed binding of platelets to PLL, IgG, anti-GP1b and collagen, but not to BSA coated surfaces. We found that under static conditions the number of cells that respond upon binding to an IgG coated surface (40 ± 7 % with Fc-receptor blocker; 41 ± 6 % without Fcreceptor blocker) was the lowest, followed by adhesion on a PLL coated surface (74 ± 7 %). On an anti-GPIb (88 ± 3 %) or a collagen coated surface (89 ± 4 %), the percentage of responding cells was similar. In addition, we found that the percentage of responding immobilized cells on a chemical stimulus was the lowest on anti-GPIb (7 ± 4 %) or collagen (6 ± 4 %), followed by an IgG coated surface with Fc-receptor blocker (39 ± 3 %) or without Fc-receptor blocker (35 ± 2 %). The percentage of cells responding to chemical stimulation was the highest on a BSA coated surface (95 ± 4 %). These measurements showed that there is a negative correlation between the percentage of cells that respond upon binding and that respond to chemical stimulation after binding. The delay times found upon binding ranged from 11 ± 8 s for platelets on PLL, followed by an anti-GPIb (29 ± 19 s) or collagen (24 ± 21 s) coated surface, and IgG coated surfaces with Fc-receptor blocker (62 ± 19 s) and without Fc-receptor blocker (51 ± 26 s). The delay times recorded on chemical stimulation were probably not sensitive enough to measure the physiological processes in adhered platelets. From the data we conclude that BSA is the most quiescent surface for platelet immobilization, while an anti-GPIb coated surface showed to be as thrombogenic as a collagen coated surface. Our experiments demonstrate that the analysis of the responding cells upon binding and chemical stimulation can discriminate between different types of platelet-surface interactions. We expect that the discrimination can be further improved e.g. by automated data processing. In conclusion, we find that the measurement of the responding fraction and the response delay time by calcium signaling are convenient methods to study the time-dependent interaction of platelets with surfaces relevant for lab-on-chip applications. Measurement of exocytosis to study platelet-surface interactions In our second approach to investigate the interaction between platelets and surfaces, we have studied the secretion process of dense granules of a cell ensemble, as well as single cell exocytosis. Adenosine triphosphate (ATP) secretion was quantified by the luminescent luciferin/luciferase reaction. Platelets were allowed to interact with BSA, PLL, mouse IgG and anti-GPIb coated surfaces, and after incubation the amount of secreted ATP was analyzed. The baseline signal was given by ATP secretion from resting platelets in suspension. ATP levels secreted from platelets immobilized on BSA were approximately 2 times as high as the baseline. The immobilization of platelets on PLL showed about 4 times baseline ATP concentrations. On IgG as well as anti-GPIb the maximum amount of ATP was secreted after 1 hour of platelet incubation. Again, we can conclude that the most quiescent surface for platelet immobilization is BSA, followed by PLL, mouse IgG and anti-GPIb. We have also studied the immobilization of the enzyme luciferase on a surface, in order to enable the detection of ATP direct at a surface. We have demonstrated that luciferase adsorbed onto PLL is indeed active and generates luminescence in the presence of ATP. However, the assay still has a low sensitivity and needs further optimization. Finally, we have investigated an exploratory method to resolve exocytosis in single platelet cells, using the fluorescent staining of the dense granules by the quinacrine dye. In our experiments we have observed that the exocytosis events are induced by the fluorescence excitation light. Very probably this is caused by the production of reactive oxygen, which disintegrates the vesicle membrane thereby releasing the vesicle content. Further studies may focus on the use of lower quinacrine concentrations, the use of lower light intensities, or on ways to scavenge reactive oxygen. It will be interesting to further develop the exocytosis assay, as a quantitative method for research on biosensor assays and surfaces suitable for biosensor applications. Conclusions and outlook The scope of the research presented in this thesis was to develop knowledge to support future technological developments, aiming at the measurement of platelet activation or responsiveness in a lab-on-chip device. We found that magnetic particles functionalized with specific antibodies can be used to measure platelet responsiveness. We have also studied the interaction of platelet with different surfaces, by an intracellular calcium signaling assay and by an ATP exocytosis assay using luciferin/luciferase. The most quiescent surface for platelets was BSA, but this surface has a low binding affinity for platelets. Anti-GPIb and collagen coated surfaces show stronger binding, but these surfaces change the activation status of the platelets. In view of these results, we have proposed a new concept to measure platelet function in a lab-on- chip device, namely by labelling platelet activation markers prior to platelet immobilization on a surface. We envision that this design will enable the sensitive labelling of platelets as well as the accurate readout of the platelets at a detection surface in the lab-on-chip device

Nacht lag auf meinen Augen (1986-87)

Hans van Zijp Nacht lag auf meinen Augen (1986-87) text by Heinrich Heine, Poem 64 of Lyrisches Intermezzo (Buch der Lieder