Studies were carried out on the mechanism responsible for the enhancement of the respiratory and secretory responses to N-formylmethionylleucylphenylalanine (fMet-Leu-Phe) exhibited by human ...neutrophils suspended in Na+-free, high-K+ buffered solution. The results demonstrate that: (a) the variation of Na+ concentration in the suspending solution induces in human neutrophils a marked modification of the recognition apparatus for the chemotactic peptide fMet-Leu-Phe, the lack of or low concentration of this ion increasing the number of the receptors and their specific affinity for the ligand; (b) the greater respiratory burst and secretion induced by fMet-Leu-Phe in human neutrophils suspended in Na+-free, high-K+ medium are due to the increased formation of receptor-ligand complexes at the cell membrane; (c) the greater respiratory response is partially due also to a higher efficiency of these receptor-ligand complexes. The molecular mechanism by which Na+ exerts a regulative role on the properties of the recognition apparatus for the chemotactic peptide and its possible significance are discussed.
A mosca-branca Bemisia tabaci Biótipo B (Hemiptera: Aleyrodidae), é um herbívoro de difícil controle devido à alta plasticidade genotípica da espécie. No tomateiro pode causar danos severos ...principalmente pela transmissão de diversas viroses. O manejo do sistema de produção e o consórcio de culturas podem ter um efeito direto nas populações desse herbívoro, sem que seja necessária a aplicação de inseticidas. Avaliou-se a influência dos sistemas de produção orgânico e convencional e o consórcio tomate-coentro na dinâmica populacional da mosca-branca no campo experimental da Embrapa Hortaliças, de maio a setembro/06. O monitoramento dos adultos da mosca-branca e de seus inimigos naturais foi realizado utilizando-se armadilhas adesivas amarelas fixadas nas bordas e no interior das parcelas experimentais e a amostragem de ninfas foi realizada por observação direta das folhas de tomate no campo. Embora as populações ao redor dos diferentes tratamentos fossem equivalentes, a abundância de adultos de mosca-branca foi significativamente menor nas parcelas de tomate consorciado com coentro, tanto no sistema convencional como orgânico. Apenas o consórcio tomatecoentro em sistema orgânico apresentou redução significativa na quantidade de ninfas por planta em relação aos demais tratamentos. Os inimigos naturais foram significativamente mais abundantes em sistema orgânico e foi verificada uma correlação negativa da abundância dos inimigos naturais e a quantidade de ninfas por planta. A associação tomate-coentro e o manejo orgânico do agroecossistema favoreceram ao controle biológico natural da mosca-branca.
Due to its high genotypic plasticity, the control of the silverleaf whitefly Bemisia tabaci B biotype (Hemiptera: Aleyrodidae), is difficult. This insect may cause severe damage to the tomato crop as a vector of several viruses. The management of the production system and the consortium with other crops may have a direct effect on this herbivore population, without the need of chemical insecticide spraying. The effect of organic and conventional production systems and the tomato-coriander consortium were evaluated in this study, in field, during May-September 2006. Adults of whitefly and its natural enemies were monitored using yellow adhesive traps installed at the edge and inside the experimental plots, and nymphs were sampled by direct observation on tomato plants. Although adult populations in the neighborhood of the different treatments were equivalent, the abundance of whitefly adults was significantly lower in the plots with the consortium tomato-coriander in both systems, conventional and organic. Significant reduction in the amount of nymphs per plant was only observed in the consortium tomato-coriander when all treatments were compared. There were more natural enemies in organic system and a negative correlation was observed between natural enemies abundance collected in the traps and whitefly nymphs' density. The association tomato-coriander and the organic management of the agroecossystem favored natural biological control of B. tabaci.
Provider: - Institution: - Data provided by Europeana Collections- Titre uniforme : La Cumparsita- BnF-Partenariats, Collection sonore - Believe- Contient une table des matières- All metadata ...published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
PDF
