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Leaf litter transport and retention in a tropical Rift Valley stream: an experimental approach 总被引:1,自引:1,他引:0
The impact of a drought on freshwater snail and trematode communities was investigated in a lake. Before the drought, 15 gastropod species (Valvatidae, Planorbidae, Lymnaeidae, Ancylidae, Physidae) and 10 trematode species (cercariaeum, xiphidiocercariae, echinostome, furcocercariae, notocotyle, lophocercous) were recorded. The rate of parasitism was 5.13% and there were 11 host species. The 2 major consequences of desiccation were the disappearance of snails, except Valvata piscinalis and Lymnaea peregra, and the absence of trematodes infecting the surviving snails. As soon as favourable conditions were restored, the littoral area was recolonized, first by hygrophilic and amphibious species, second by aquatic species. Nine months after the drought, the gastropod community was restored. Recolonization by the trematodes was delayed compared with that of gastropods. During the study, the overall prevalence was equal to 0.36% and only 4 trematode species and 5 host species were recorded. Because of the great variability of freshwater ecosystems, long-term studies are necessary to understand the dynamics of snail and trematode populations and determine the regulatory effect of parasitism in the field. 相似文献
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D'Antoni S Zambusi L Codazzi F Zacchetti D Grohovaz F Provini L Catania MV Morara S 《Neurochemical research》2010,35(12):2135-2143
Previous reports described the transient expression during development of Calcitonin Gene-Related Peptide (CGRP) in rodent
cerebellar climbing fibers and CGRP receptor in astrocytes. Here, mixed cerebellar cultures were used to analyze the effects
of CGRP on Purkinje cells growth. Our results show that CGRP stimulated Purkinje cell dendrite growth under cell culture conditions
mimicking Purkinje cell development in vivo. The stimulation was not blocked by CGRP8-37, a specific antagonist, suggesting
the activation of other related receptors. CGRP did not affect survival of Purkinje cells, granule cells or astrocytes. The
selective expression of Receptor Component Protein (RCP) (a component of CGRP receptor family) in astrocytes points to a role
of these cells as mediators of CGRP effect. Finally, in pure cerebellar astrocyte cultures CGRP induced a transient morphological
differentiation from flat, polygonal to stellate form. It is concluded that CGRP influences Purkinje cell dendrite growth
in vitro, most likely through the involvement of astrocytes. 相似文献
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