Growth

The overall growth of the regenerating arms of A. mediterranea was significantly affected by PCBs, 4-NP and TPT-Cl exposure in comparison with control animals (Candia Carnevali et al. 2001a,b; 2003; Barbaglio et al. 2004). However, contrasting results were obtained for the three classes of chemicals: in fact, some compounds accelerated the regenerative growth, whereas others appreciably inhibited the regrowth process. As far as PCB exposure is concerned, if during the early regenerative phase (72 h post-amputation) the exposed samples did not show significant anomalies in terms of growth and development, at the advanced regenerative phase (1-2 weeks post-amputation) an unusual accelerated growth was clearly evident in all the exposed arms in comparison with the growth of the standard regenerating arms at the same stages (Fig. 4a,b,e,f). This involved the overall size of the regenerating arm, which appeared much more developed, and the differentiation of its anatomical structures, external or internal, such as the lateral pinnules and the brachial skeletal components (ossicles). In contrast, 4-NP appeared to cause an appreciable delay in the overall growth of the regenerating blastema observable with all the exposure concentration tested (Fig. 4a,d,e,g). With regard to TPT-Cl-exposed samples, a clear effect in terms of enhanced growth, even though less marked than that of PCB samples, could be also detected (Fig. 4a,c,e,h). A quantitative analysis carried out in parallel with the qualitative morphological analysis on the measured lengths of all the experimental regenerates, in both exposed and control samples, showed that in terms of average overall sizes of the regenerating arms, a clear correlation between growth and exposure could be observed for all the test compounds: the differences in the overall growth were particularly evident at 2-week postamputation; at this stage, which corresponded to a long-term exposure period, the exposed samples also displayed a remarkable variability in terms of overall growth if compared with the uniform standard size of the controls. Quantitative data showed that in PCB-exposed samples the growth increase was significant at both 1 week and 2 weeks post-amputation (Candia Carnevali et al. 2001a,b), whereas in TPT-Cl-exposed samples a significant effect in terms of enhanced growth could be detected only at the advanced stage of 2 weeks and with the higher concentration employed (225 ng/l) (Barbaglio et al. 2004).

Fig. 4a-h. Whole mount stereomicroscopic views of control and exposed regenerating arms of Antedon mediterranea at different stages. Exposure concentrations: PCB: 14 ng/l; 4-NP: 2 |g/l; TPT-Cl: 100 or 225 ng/l. a-d 1 week pa (post-amputation): a control sample; b PCB-exposed sample; c TPT-Cl-exposed sample; d 4-NP-exposed sample. In the PCB-

exposed sample, abnormal growth of the regenerate and advanced development of its anatomical features are evident. In the TPT-Cl- and 4-NP-exposed samples, delayed and anomalous regrowth is evident. Arrow Brachial ossicles; double arrowheads pinnules. Insets show details of the respective regenerating arms from SEM. a and b, bars 240 |m; inset bars 100 |m. e-h Regenerating arms at 2 weeks pa: e control sample; f PCB-exposed sample; g 4-NP-exposed sample; h TPT-Cl-exposed sample. Growth of the PCB-exposed sample is more pronounced than in the controls, whereas that of the 4-NP and TPT-Cl samples is markedly delayed. In addition, 4-NP and TPT-Cl samples show evident malformations. This can be appreciated in terms of both overall size and shape of the regenerate and differentiation of anatomical structures. Bars 240 |m (e, g and h); 250 |m (f)

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