Détermination de la DL 50

The occurrence of a resistance phenomenon in Varroa jacobsoni can be shown by comparing the LD50 of an acaricide formula over time. This work proposes a simple method for determining the LD5 0 and applies it to 2 compounds: Antivarroa®(Schering) and Perizin® (Bayer). Tests were made in polycarbonate boxes which were changed each time. Temperature was 26-28 °C, humidity 70%. Varroa mites were taken from infested bees with a paintbrush and immobilized on a foam-rubber bed. 0.25 ml of an acaricide solution was applied via a microsyringue. The mites were then replaced on the bees. Each box contained 20 infested bees and 10 non-infested bees. Different solutions of the acaricide were tested to determine a toxicity curve and to calculate the LD50 after 24 h by the method of Lichtfield and Wilcoxon (Thalarida and Murry, 1988). The mean LD 50 of Anti-varroa® was 17.3 pg per varroa (11.7-25.6 pg per Varroa; P < 0.05). The LD50 of amitraz in the product Anti-varroa® was 2.16 pg per Varroa (1.46-3.2 pg). The mean LD50 of Perizin® was 98.4 pg per varroa (79.1-122.3 pg per Varroa; P< 0.05). The LD50 of coumaphos in the product Perizin® was 3.15 pg per Varroa (2.53-3.91 pg). The experimental conditions must be accurate in order to obtain reproducible or comparable results: the area where the acaricide solution is deposited must be precisely defined and the reading time specified. Commercial products were used in this study because excipients may influence the toxicity of the active ingredients. This method, using free Varroa mites on bees is more representative of the actual field conditions than methods using isolated mites

Activite des huiles essentielles de labiees sur Ascophaera apis et traitement d'un rucher

National audienc

Activité des huiles essentielles de Labiées sur Ascophaera apis et traitement d'un rucher

International audienc

Activite des huiles essentielles de labiees sur Ascophaera apis et traitement d'un rucher

National audienc

Activité des Huiles Essentielles de Labiées sur Ascophaera apis et Traitement d\u27un Rucher

International audienc

Retinal vein occlusions : the potential impact of a dysregulation of the retinal veins

A retinal vein occlusion (RVO) is a sight threatening disease. It can be divided into central vein occlusion and branch retinal vein occlusion. The pathogenesis of the condition remains to be solved. Mechanical compression of the vessel wall or thrombotic occlusion of the vessel lumen, sometimes combined with rheological disorders, are often assumed pathomechanisms. Accordingly, the therapy relies either on mechanical decompression, lyses of thrombi or improvement of rheology. A number of observations however, such as the relationship of RVO to atherosclerotic risk factors, spontaneous reversibility particularly in young patients, rest flow observed in angiography, occlusion despite anticoagulation or thrombocytopenia and finally the positive effect of anti-VEGF therapy are not explained by the present pathogenetic concept. As a new concept we propose a local venous constriction induced by vasoconstrictive molecules diffusing from neighbouring diseased arteries and/or from other neighbouring (hypoxic) tissues. Recognizing these postulated conditions might lead to an earlier identification of impending vein occlusions as well as to a treatment more tailored to the risk factor constellation of the particular patient