Immunolocalization of G-protein alpha subunits in the olfactory system of the cartilaginous fish Scyliorhinus canicula.

In the olfactory and vomeronasal systems of vertebrates, the morphology of the receptor neurons, the receptor gene family they express, the G-protein coupled with the receptor (in particular the G-protein alpha subunit), and their projection to the olfactory bulb are correlated. Much information about this complicated system have been collected in different groups, but nothing is known about Chondrichthyes. In this work, the presence and distribution of immunoreactivity for different types of G-protein alpha subunit (Galpha(o), Galpha(q) and Galpha(s/olf)) were investigated in the olfactory mucosa and olfactory bulb of the shark Scyliorhinus canicula. Only Galpha(o)-like immunoreactivity was detected in the olfactory mucosa and bulb, both in tissues and homogenates. Its distribution was partially similar to that found in other vertebrates: it was localized in the microvillous receptor neurons, in numerous axon bundles of the fila olfactoria, in the stratum nervosum and in the most of glomeruli in the stratum glomerulosum. No immunoreactivity was instead observed in the crypt neurons, the second type of olfactory neurons present in cartilaginous fish. The projections of crypt neurons to olfactory bulb probably correspond to the few ventrally-located glomeruli which were negative to the antiserum against Galpha(o). These data suggest, in S. canicula, different olfactory neuron types send projections to the olfactory bulb with a segregated distribution, as observed in other vertebrates.

Echinoderm regenerative response as a sensitive ecotoxicological test for the exposure to endocrine disrupters: effects of p,p'DDE and CPA on crinoid arm regeneration.

Echinoderms are valuable test species in marine ecotoxicology and offer a wide range of biological processes appropriate for this approach. Regenerating echinoderms can be regarded as amenable experimental models for testing the effects of exposure to contaminants, particularly endocrine disrupter compounds (EDCs). As regeneration is a typical developmental process, physiologically regulated by humoral mechanisms, it is highly susceptible to the action of pseudo-hormonal contaminants which appear to be obvious candidates for exerting deleterious actions. In our laboratory experiments, selected EDCs suspected for their antiandrogenic action (p,p'-DDE and cyproterone acetate) were tested at low concentrations on regenerating specimens of the crinoid Antedon mediterranea. An integrated approach which combines exposure experiments and different morphological analyses was employed; the obtained results suggest an overall pattern of plausible endocrine disruption in the exposed samples, showing that processes such as regenerative growth, histogenesis, and differentiation are affected by the exposure to the selected compounds. These results confirm that (1) regenerative phenomena of echinoderms can be considered valuable alternative models to assess the effects of exposure to exogenous substances such as EDCs, and (2) these compounds significantly interfere with fundamental processes of developmental physiology (proliferation, differentiation, etc...) plausibly via endocrine alterations. In terms of future prospects, taking into account the increasing need to propose animal models different from vertebrates, echinoderms represent a group on which ecotoxicological studies should be encouraged and specifically addressed.