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During early development in vertebrates, Sonic hedgehog (Shh) is produced by the notochord and the floor plate. A ventrodorsal gradient of Shh directs ventrodorsal patterning of the neural tube. However, Shh is also required for the survival of neuroepithelial cells. We show that Patched (Ptc) induces apoptotic cell death unless its ligand Shh is present to block the signal. Moreover, the blockade of Ptc-induced cell death partly rescues the chick spinal cord defect provoked by Shh deprivation. Thus, the proapoptotic activity of unbound Ptc and the positive effect of Shh-bound Ptc on cell differentiation probably cooperate to achieve the appropriate spinal cord development.

The human KAL gene is responsible for the X chromosome-linked Kallmann syndrome. A partial cDNA sequence from the chicken KAL homologue was determined and used to study expression of the KAL gene, by in situ hybridization, during chicken development, from day 6 of incubation. The KAL gene is mainly expressed in neurons of the central nervous system during the second half of embryonic life. High levels of transcript were detected in mitral neurons of the olfactory bulbs, in striatal neurons, in Purkinje cells of the cerebellum, in retinal neurons, and in isolated neurons of the brainstem and spinal cord. No expression was observed in glial cells. A low level of expression was observed in some mesenchymal derivatives. In the adult, expression is maintained or increased in several neuronal populations, especially in optic tectum and striatum. A possible role for the KAL protein in synaptogenesis at these stages is discussed. These results in the chicken embryo help to elucidate the mechanisms of anosmia and gonadotropin-releasing hormone deficiency, which define Kallmann syndrome. In addition, most of the occasional symptoms described in Kallmann syndrome patients, such as cerebellar ataxia, abnormal ocular movements, abnormal spatial visual attention, mirror movements, and renal aplasia, could be ascribed to malfunction of areas that, in the chicken, express the KAL gene.

Many countries have introduced health impact assessment (HIA) at the national, regional, or local levels. In France and in Québec, there is increasing interest in using HIA to inform decision-makers and influence policies, programs, and projects. This paper aims to compare HIA implementation models in two regions: Nouvelle-Aquitaine (France) and Montérégie (Québec, Canada) using a case study methodology. The objective is to gain a better understanding of the similarities and differences in the approaches used to achieve the operationalization of HIA. The methodological approach involves four steps: (1) design of an analytical framework based on the literature; (2) exchanges within the research team and review of documents concerning the two implementation strategies under study; (3) development of the case studies based on the proposed framework; and (4) cross-comparison analysis of the case studies. The findings show that the two regions share certain similarities, including the strong commitment and political will of the public health organizations involved and a well-established culture of engaging in intersectoral action with municipal partners. Differences mainly concern their different approaches to implementing HIAs in accordance with the regional policies and the organizational and administrative contexts in place. This study identifies potential avenues for supporting the practice of HIA at the municipal level.