A hierarchy of determining factors controls motoneuron innervation

Quail leg buds were grafted in place of chick leg buds or chick wing buds and vice versa at stages 18 to 21 after colonization by muscle precursor cells had been completed. Motor endplate pattern in the plantaris muscle of the grafts was analyzed before hatching by means of esterase and acetylcholinesterase staining techniques. Muscle fibre types were made visual using the myosin ATPase reaction. Investigations are based on the species-specific endplate pattern of the plantaris muscle: multiply innervated fibres in the chick and focally innervated fibres in the quail. Muscle pieces isolated from the adjacent medial gastrocnemius muscle of the grafted legs were histologically examined to judge their species-specific composition. Horseradish peroxidase was injected into the plantaris muscles of both the grafted and the opposite leg as well as in the plantaris muscle of normal quail embryos, in order to be sure that the plantaris muscle of the graft is innervated by appropriate motoneurons. This procedural design offers for the first time a possibility to test experimentally the influences of motoneurons on endplate pattern formation under conditions corresponding to those in normal ontogenesis. It is shown that such appropriate motoneurons of one species which project to the plantaris muscle of the other species dictate the endplate pattern. When the plantaris muscle is innervated by inappropriate motoneurons, the endplate pattern inherent in the muscle primordium itself becomes realized. A sequence of hierarchically acting factors is proposed to bring different results in line. According to this, the neuronally set programme has priority compared with that set in the muscle. This is true for the normal development and might generate the high neuro-muscular specificity. If under experimental conditions the neuronal programme and the peripheral programme differ, the axons and muscle fibres selectively interact with respect to their inherent characteristics and the muscle-specific programme becomes expressed. If there is a lack of a certain axon type, muscle fibres might become innervated by non-corresponding motoneurons which alter the muscle fibre type.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47522/1/429_2004_Article_BF00309770.pd

Hydrologie, paludisme et démoustication. (L'exemple de la Région Rhône-Alpes) / Hydrology, malaria and mosquito control : the example of the Rhône-Alpes region, France

Abstract : Hydrology, malaria and mosquito control: the example of the Rhône-Alpes region, France. After analysing historical documents concerning the presence of malaria during the 18th and 19th centuries in the French alpine piedmont (Forez and Dombes wetlands, floodplains of Rhone river and its tributaries), the authors show that the outbreak of the disease in the middle of the last century was a short-term consequence of civil engineering works, the marked increase in mosquito populations resulting from the modification of hydrological parameters associated with the diking of flood- plains. The reasons for the disappearance of malaria around 1883 are discussed and the authors point out that mosquito species capable of transmitting the plasmodium are still present today in the wetlands of the Rhône-Alpes region.Résumé : Après avoir analysé les chroniques se rapportant au paludisme en région Rhône Alpes aux XVIIIe et XIXe siècles, les auteurs montrent que la recrudescence de cette maladie en Savoie, au milieu du siècle dernier, était, en fait, une conséquence (impact à court terme) des travaux de génie civil réalisés dans les plaines alluviales. Les raisons qui auraient entraîné la disparition des « fièvres paludéennes » vers 1883 sont analysées. On montre que les vecteurs transmettant le plasmodium existent encore dans la zone d'étude. L'éventualité de la réapparition de la maladie et la nécessité de limiter les populations de moustiques dans les zones humides du piedmont alpin sont discutées.Pautou Guy, Girel Jacky, Pautou M. P., Gruffaz René. Hydrologie, paludisme et démoustication. (L'exemple de la Région Rhône-Alpes) / Hydrology, malaria and mosquito control : the example of the Rhône-Alpes region, France. In: Revue de géographie alpine, tome 83, n°1, 1995. pp. 33-52

Toxicity of vegetable tannins on Crustacea associated with alpine mosquito breeding sites

International audienceThe impact of tannins from the environmental vegetation naturally polluting Alpine mosquito breeding sites was experimentally investigated by studying the toxicity of tannic acid, a natural hydrolyzable tannin, on the nontarget crustacean fauna associated with culicine populations. Bioassays indicate that exposure to tannic acid at concentrations from 0.06 to 2.0 mM is more deleterious to Chydorus sphaericus, Diaptomus castor, and Eucypris fuscata, than to Daphnia pulex, Acanthocyclops robustus, and Eucypris virens. Histopathological investigations after treatment with tannic acid at concentrations from 0.125 to 0.500 mM reveal sequential degenerative patterns of the midgut epithelium depending on the taxon, duration of the treatment, and concentrations assayed, These differential toxic effects on Crustacea are compared with those previously observed in larval Dipteral in order to evaluate the plant tannins as potentially useful products in integrated mosquito management programs. (C) 2000 Academic Press

Differential toxicity of leaf litter to dipteran larvae of mosquito developmental sites

International audienceThe relative toxicity of leaf litter to nematocerous dipteran larvae characteristic of mosquito developmental sites was investigated. Culicidae, Chironomidae, and Simuliidae taxa originating from alpine hydrosystems were tested together with two laboratory nonindigenous culicid taxa. Bioassays indicate that ingestion of 10-month-old decaying leaves from Alnus glutinosa, Populus nigra, and Quercus robur by larvae is more deleterious for Aedes aegypti, A. albopictus, Culex pipiens, Simulium variegatum, and Chironomus annularius than for A. rusticus. Histopathological observations reveal that the midgut epithelium is the main target organ of the toxic effect of dietary leaf litter, which appears to be stronger than that of previously reported tannic acid. There is a general response of the nematocerous larval midgut epithelium to dietary tannins-phenolic compounds: clear cells of the anterior midgut showing symptoms of intoxication before dark cells of the posterior midgut. (C) 2000 Academic Press

Role of vegetable tannins in habitat selection among mosquito communities from the Alpine hydrosystems

International audienceThe role of vegetable tannins in habitat selection among mosquito communities in Alpine hydrosystems was investigated through ecotoxicological comparison of 19 arthropod species characteristic of 12 breeding sites known for their abiotic environmental factors and their different riparian vegetation. The toxicity of tannins was experimentally compared among species representative of both the dipteran fauna and the crustacean fauna associated with the mosquito breeding sites. Bioassays using tannic acid solutions at concentrations from 0.1 to 11 mM separated the dipteran taxa into five groups of differential sensitivity and the crustacean taxa into four groups. The different levels of sensitivity among taxa were correlated with the various amounts of total phenolics and tannins found in the most prominent plant types associated with the different breeding sites. This suggested that tannins and, more generally, phenolic compounds may be involved in plant-arthropod interactions in Alpine hydrosystems. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS