Effects of Neurotoxic Compounds on P lividus Ion Dynamics

From this point of view, the early phases of sea urchin development offer very good material for the preparation of biosensors based on living cells, because the effects on the cholinergic system are per se translated into changes in membrane potential. Actually, by exposing P. lividus zygotes to diazinon, an OP compound, we found that the increase in [Ca2+]j, either caused by mus-carinic drug exposure or the physiological one preceding the NEB, was prevented. The K+ outward channel probably linked to excitation of the muscarinic receptor m2 was also blocked by highly diluted phentoate, another OP compound commonly used as an insecticide (Percivale 2003).

This offers the possibility of adapting this model to a biosensor capable of recording the impedance changes by using P. lividus zygotes (the moment when the cholinergic system is mostly dependent on electrical variations) (Fig. 9).

The employment of these cells is at present innovative, as well as bioethi-cally compatible. In addition, it may solve some controversial points, such as: 1. The problem of experiments on animals, which are more expensive, besides causing pain, which is particularly evident in higher organisms. Gametes from sea urchins may be obtained easily by intra-oral 1/1,000 ACh injection: this treatment allows gamete spawning without sacrificing the adults, which survive in good health (as demonstrated by further natural spawning in a few weeks: M. Franzoni and M. Sgro, preliminary results, pers. comm.).

zygote, free from the fertilisation envelope mount for electrode zygote, free from the fertilisation envelope mount for electrode

Fig. 9. A Schematic drawing of the living cell-based biosensor (IBMT). B The micro-device for impedance recording

2. The improved knowledge of developmental biology, within the emerging knowledge that neurotransmitter molecules are not limited to neuromus-cular structures, but are generally involved in cell-to-cell communication, leading to interaction between developing cells and tissues.

3. Exporting the results to other organisms, including man, by comparing the effects on P.lividus zygotes with the effects on human stem cells (addressed to development).

4. Allowing us to establish conversion parameters among the different cell sources, in order to use the most suitable and available for each situation of risk assessment.

Acknowledgements. This work was supported by the EC within the project SENS-PESTI, QLK4-CT-2002-02264. We thank Dr. Mario Franzoni and Dr. Marco Sgro for allowing us to use their preliminary data on rearing sea urchin specimens; and Dr. Mario Mori for continuous supply of living sea urchins in optimal reproductive conditions.

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