Screening by different means has demonstrated the presence, in human and murine neuroblastoma cell lines, of VGF, a gene product identified in a limited number of neuronal and endocrine cells. Indirect immunofluorescence and Western and Northern blot analyses have shown the presence of this protein in some of the tested lines, confirming that VGF is not an ubiquitous molecule. Further studies, using human SK-N-BE and murine N18TG2 lines, showed that VGF expression is upregulated during differentiation, suggesting that various species, including man, express VGF and regulate it in a similar manner. The subcellular localization of the protein, which is associated with vesicles, its electrophoretic molecular profile and its specific release under different conditions are all consistent with results reported in other cells. Neuroblastomas are thus added to the class of VGF-positive cells and provide a new in vitro model for investigation of the structural and functional properties of this protein.
Data from the literature demonstrate the existence of a growing family of neuropoietic cytokines; members of this group have structural motifs in common with other members and with neurotrophic factors. In this research we studied the responses elicited in vitro by some of these molecules in two different neuronal populations: murine neuroblastoma N18TG2 and neurons from chicken dorsal root ganglia. Both IL-2 and IL-6 improve the survival of murine neuroblastoma cells in clonal density plating experiments; in addition IL-2 significantly inhibits thymidine incorporation by single cell suspension. The survival of sensory neurons, on the other hand, non-responsive to IL-2 and IL-6, was significantly supported by IL-3, which also stimulates their morphological differentiation, inducing the formation of a well-developed neural net. In conclusion, results reported here confirm the neurotrophic activity of some ILs and provide additional neuronal models for future investigations.
The presence of acetylcholinesterase has been detected in the thymus of several species both biochemically and histochemically. In this study we have investigated the molecular forms and the level of this enzyme in separate compartments of the murine thymus and in different thymocyte subpopulations. Similar levels of acetylcholinesterase activity are present both in thymocytes and in the stromal component. Sucrose density gradient analysis revealed the presence of a single molecular form of about 5 S, presumably a dimeric form. Moreover the results demonstrate a preferential association of AChE with mature thymocyte subsets (Peanut Agglutinin negative and Corticoresistant). This finding correlates with the preferential sensitivity of these cells to cholinergic drugs and supports the hypothesis that acetylcholinesterase modulates the cholinergic effects on thymocytes.
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