Primary anthelmintic screening: systems for the evaluation of in vitro anthelmintic activity

Los nematodos parásitos causan enfermedades importantes al hombre y a los animales domésticos. El control de estas infecciones se apoya fundamentalmente en el tratamiento con antihelmínticos; lamentablemente, se han ido desarrollando resistencias frente a las distintas clases de antihelmínticos de amplio espectro y existe una clara necesidad de encontrar nuevas alternativas terapéuticas. La investigación farmacológica tiene indudablemente un requerimiento básico: disponibilidad de sistemas de valoración rápidos, sencillos y económicos. En esta revisión examinaremos los métodos que se han propuesto para la evaluación in vitro de actividad nematocida. En ellos se utilizan nematodos de vida libre y nematodos parásitos (estadios de vida libre y de vida parasitaria). La actividad se valora determinando el efecto de los productos objeto de estudio sobre el desarrollo, la viabilidad o la motilidad de distintos estadios, o bien a través de parámetros bioquímicos. Estos métodos varían en su sensibilidad, capacidad de selección, rapidez, coste y facilidad de ejecución pero en muchos casos pueden constituirse en sistemas adecuados para la preselección, previa al cribado primario en modelos animales, de antihelmínticos potenciales.Nematode parasites cause serious infectious diseases in humans and domestic animals. Control of these infections relies mostly on chemotherapeutics, but resistance has developed against most of these broad-spectrum drugs in many parasite species. Discovery and development of new agents effective against the nematodes of major economic or medical importance is necessary now. An important basic requirement for the discovery of chemotherapeutic drugs is the testing facilities. In this paper, in vitro techniques used for the detection and measurement of anthelmintic activity are reviewed. The primary systems employed for this purpose utilize free-living nematodes and free-living and parasitic stages of parasitic nematodes. Interpretation of nematocidal activity in these assays commonly relied on the detection of drug-induced effects on nematode development, viability, motility or biochemical parameters. Such screens vary in their sensitivity, selectively, cost, rapidity and ease of execution, but afford useful and economical means for the initial selection of new compounds for further more detailed evaluation in animal models.Facultad de Ciencias Veterinaria

Primary anthelmintic screening: systems for the evaluation of in vitro anthelmintic activity

Los nematodos parásitos causan enfermedades importantes al hombre y a los animales domésticos. El control de estas infecciones se apoya fundamentalmente en el tratamiento con antihelmínticos; lamentablemente, se han ido desarrollando resistencias frente a las distintas clases de antihelmínticos de amplio espectro y existe una clara necesidad de encontrar nuevas alternativas terapéuticas. La investigación farmacológica tiene indudablemente un requerimiento básico: disponibilidad de sistemas de valoración rápidos, sencillos y económicos. En esta revisión examinaremos los métodos que se han propuesto para la evaluación in vitro de actividad nematocida. En ellos se utilizan nematodos de vida libre y nematodos parásitos (estadios de vida libre y de vida parasitaria). La actividad se valora determinando el efecto de los productos objeto de estudio sobre el desarrollo, la viabilidad o la motilidad de distintos estadios, o bien a través de parámetros bioquímicos. Estos métodos varían en su sensibilidad, capacidad de selección, rapidez, coste y facilidad de ejecución pero en muchos casos pueden constituirse en sistemas adecuados para la preselección, previa al cribado primario en modelos animales, de antihelmínticos potenciales.Nematode parasites cause serious infectious diseases in humans and domestic animals. Control of these infections relies mostly on chemotherapeutics, but resistance has developed against most of these broad-spectrum drugs in many parasite species. Discovery and development of new agents effective against the nematodes of major economic or medical importance is necessary now. An important basic requirement for the discovery of chemotherapeutic drugs is the testing facilities. In this paper, in vitro techniques used for the detection and measurement of anthelmintic activity are reviewed. The primary systems employed for this purpose utilize free-living nematodes and free-living and parasitic stages of parasitic nematodes. Interpretation of nematocidal activity in these assays commonly relied on the detection of drug-induced effects on nematode development, viability, motility or biochemical parameters. Such screens vary in their sensitivity, selectively, cost, rapidity and ease of execution, but afford useful and economical means for the initial selection of new compounds for further more detailed evaluation in animal models.Facultad de Ciencias Veterinaria

Rod-sphere cluster irradiation with femtosecond laser pulses: Cut and paste at the nanoscale

We report on the irradiation of gold rod–sphere assemblies with ultrashort laser pulses, producing structures that are very difficult to obtain by other methods. The optical response of these assemblies displays several peaks arising from the interaction of the plasmon modes of the individual particles, offering thus great flexibility to control the energy deposited on the individual particles. Judicious selection of the wavelength and fluence of the laser pulses allow fine control over the changes produced: the particles can be melted, welded and/or the organic links cleaved. In this way, it is possible to generate structures “à la carte” with a degree of control unmatched by other synthetic protocols. The method is exemplified with gold nanoparticles, but it can be easily implemented on particles composed of different metals, widening considerably the range of possibilities. The final structures are excellent candidates for surface-enhanced spectroscopies or plasmonic photothermal therapy as they have a very intense electric field located outside the structure, not in the gaps

Automated imaging and other developments in whole-organism anthelmintic screening.

Helminth infections still represent a huge public health problem throughout the developing world and in the absence of vaccines control is based on periodic mass drug administration. Poor efficacy of some anthelmintics and concerns about emergence of drug resistance has highlighted the need for new drug discovery. Most current anthelmintics were discovered through in vivo screening of selected compounds in animal models but recent approaches have shifted towards screening for activity against adult or larval stages in vitro. Larvae are normally available in greater numbers than adults, can often be produced in vitro and are small enough for microplate assays. However, the manual visualization of drug effects in vitro is subjective, laborious and slow. This can be overcome by application of automated readouts including high-content imaging. Incorporated into robotically controlled HTS platforms such methods allow the very large compound collections being made available by the pharmaceutical industry or academic organizations to be screened against helminths for the first time, invigorating the drug discovery pipeline. Here, we review the status of whole-organism screens based on in vitro activity against living worms and highlight the recent progress towards automated image-based readouts

Some hydrolase activities from the tick Hyalomma lusitanicum

In this work has been made a detection and preliminary characterization of some hydrolases in whole extracts from unfed adult males and females of Hyalomma lusitanicum, one of the vectors for Theileria annulata that causes Mediterranean theileriosis in cattle. We have elected as targets, proteases as enzymes implicated in the nutritional processes of ticks, esterases that are usually implicated in resistance to organophosphates and phosphatises often implicated in protein phosphorilation and control of ticks salivary gland. The biological role and physiological significance are discussed in terms of the possibility of use these enzymes as possible in future anti-tick vaccination or acaricide resistance

Some hydrolase activities from the tick

In this work has been made a detection and preliminary characterization of some hydrolases in whole extracts from unfed adult males and females of Hyalomma lusitanicum, one of the vectors for Theileria annulata that causes Mediterranean theileriosis in cattle. We have elected as targets, proteases as enzymes implicated in the nutritional processes of ticks, esterases that are usually implicated in resistance to organophosphates and phosphatises often implicated in protein phosphorilation and control of ticks salivary gland. The biological role and physiological significance are discussed in terms of the possibility of use these enzymes as possible in future anti-tick vaccination or acaricide resistance

SHORT COMMUNICATION - Ivermectin Resistant and Susceptible Third-stage Larvae of Haemonchus contortus: Cholinesterase and Phosphatase Activities

Cholinesterase and acid phosphatase (AP), but not alkaline phosphatase activities, were detected in cytosolic and membrane-bound fractions of ivermectin resistant and susceptible Haemonchus contortus infective-stage larvae. Some differences in acetylcholinesterase activity of cytosolic fractions and in the AP activity of these fractions as well as in the response to AP inhibitors by membrane-bound fractions were detected. Data are discussed