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Paramecium primaurelia is a unicellular eukaryote that moves in freshwater by ciliary beating and responds to environmental stimuli by altering motile behaviour. The movements of the cilia are controlled by the electrical changes of the cell membrane: when the intraciliary Ca2+ concentration associated with plasma membrane depolarization increases, the ciliary beating reverses its direction, and consequently the swimming direction changes. The ciliary reversal duration is correlated with the amount of Ca2+ influx. Here, we evaluated the effects due to the activation or blockade of N-methyl-D-aspartic acid (NMDA) receptors on swimming behaviour in Paramecium. Paramecia normally swim forward, drawing almost linear tracks. We observed that the simultaneous administration of NMDA and glycine induced a partial ciliary reversal (PaCR) leading to a continuous spiral-like swim. Furthermore, the duration of continuous ciliary reversal (CCR), triggered by high external KCl concentrations, was longer in NMDA+glycine-treated cells. NMDA action required the presence of Ca2+, as the normal forward swimming was restored when the ion was omitted from the extracellular milieu. The PaCR and the enhancement of CCR duration significantly decreased when the antagonists of the glutamate site D-AP5 or CGS19755, the NMDA channel blocker MK-801 or the glycine site antagonist DCKA was added. The action of NMDA+glycine was also abolished by Zn2+ or ifenprodil, the GluN2A and the GluN2B NMDA-containing subunit blockers, respectively. Searches of the Paramecium genome database currently available indicate that the NMDA-like receptor with ligand-binding characteristics of an NMDA receptor-like complex, purified from rat brain synaptic membranes and found in some metazoan genomes, is also present in Paramecium. These results provide evidence that functional NMDA receptors similar to those typical of mammalian neuronal cells are present in the single-celled organism Paramecium and thus suggest that the glutamatergic NMDA system is a phylogenetically old behaviour-controlling mechanism.

The aim of this study was to investigate the possible impact of silver nanoparticles (Ag-NPs) on reproduction and development of different model organisms, such as sea urchins, barnacles, brine shrimps and zebrafish. In vivo toxicological tests were performed; the biological models were exposed to serial dilutions of commercial Ag-NPs. Our findings revealed that: i) all tests were suitable to verify the impact of Ag-NPs on models in term of exposure; ii) all tests can provide an idea of the role of NPs on environmental health; iii) an integrated interdisciplinary approach, using several model organisms, is recommended in order to have an overview of the effects of NPs on water environment., Le but de cette étude était d'étudier le possible impact des nanoparticules d'argent (Ag-NP) sur la reproduction et le développement des différents modèles des organismes, tels que les oursins, les balanes, les crevettes de saumure et le poisson zèbre. Des tests toxicologiques ont été réalisées in vivo, les modèles biologiques ont été exposés à des dilutions successives de Ag- NP commerciale. Nos résultats ont révélé que: i) tous les tests ont permis de vérifier l'impact de l'Ag-IP sur des modèles en terme d'exposition, ii) tous les tests ont donné une idée du rôle des IP sur la santé de l'environnement; iii) une approche intégrée et interdisciplinaire, utilisant plusieurs des organismes modèles, est recommandé afin d'avoir un aperçu des effets des NP sur l'environnement aquatique., Lo scopo di questo lavoro è stato valutare l’impatto delle nanoparticelle di argento (Ag-NPs) sulla riproduzione e sullo sviluppo di vari organismi modello, quali Paracentrotus lividus, Amphibalanus amphitrite, Artemia salina e Danio rerio. Sono stati eseguiti test tossicologici mediante esposizione in vivo; i modelli sono stati esposti a diluizioni seriali di Ag-NPs commerciali. I risultati hanno dimostrato che: i) i test utilizzati sono adatti a verificare l’impatto delle Ag-NPs sui modelli a seconda delle esposizioni; ii) l’impatto sugli organismi e, quindi sulla salute ambientale, è dose e tempo-dipendente; iii) l’approccio integrato tra diversi modelli permette una valutazione predittiva dell’impatto delle nanoparticelle sull’ambiente acquatico., EQA - International Journal of Environmental Quality; Vol 8 (2012); 61-65

Imaging of Endocytosis in Paramecium by Confocal Microscopy

We detected the effect of Cadmium on the cytoskeleton of Clathrina clathrus by immunocytochemistry, confocal microscopy and immunoblotting. Results highlighted the potential of the sponge to resist to the action of heavy metals through the reorganisation of the tubulins and suggest the utilization of sponges for biomonitoring of environmental pollution.