No abstract

Our findings suggest that, in aging uncomplicated by disease, nutritional status is similar to that in younger adults, although the range of values tended to be wider, with a higher risk of certain nutrient deficiencies.

The retinoids are the natural and synthetic analogues of retinol or vitamin A. These molecules are able to modulate differentiation and proliferation processes in several cell types. The presence of retinoids is essential for inducing or maintaining the differentiation of epithelial cells. On the other hand, when excess retinol is added to the culture medium, the differentiation of some mesenchymal cells is impaired. Retinoids also promote the differentiation of carcinoma cells of various origins: embryonal carcinoma, leukaemic and melanoma cells. While their effect on the proliferation of normal cells appears variable, these molecules inhibit the growth of cells treated with a tumoural promoter, or spontaneously transformed cells, and they prevent tumour promotion. Various mechanisms of action might be involved: retinoids could act at the level of the genome with or without the participation of their binding proteins. They might also influence glycoconjugate biosynthesis and interact, through certain glycosylation reactions, with growth factor receptors. The role of vitamin A and its structural analogues in cell differentiation and growth is of great therapeutic interest.After a brief reminder of the structure and metabolism The neoplastic process is characterized by an alter-of the retinoids we shall go on to discuss first the ation of the differentiated histological state of cells effect of these compounds on the differentiation of towards metaplastic and anaplastic forms and is as-various cell types (of epithelial, mesenchymal and sociated with cellular proliferation which escapes the cancerous origin). We shall then study the influence usual homeostatic control systems.of the retinoids on the proliferation