“…On the contrary, primary cell cultures have unstable phenotypes, and may quickly lose many differentiated functions. The use of immortalized and continuous cell lines offers ease of propagation, and the ability to generate unlimited numbers of cells for testing (Speilman et al, 1998;Pfaller and Gstraunthaler, 1998;Costa, 1998). Many different cell types have been used in toxicity studies, including continuous renal epithelial cell lines to assess nephrotoxicity (Pfaller and Gstraunthaler, 1998;Prieto, 2002), neuroblastoma or glioma cell lines to assess neurotoxicity (Costa, 1998;Lindahl et al, 1999;Tahti et al, 2003;Madia et al, 2004), embryonic stem cells and ovarian and testicular cell types to assess reproductive and developmental toxicity (Spielmann, 1998;Riecke and Stahlmann, 2000;Bishop, 2003;Bremer et al, 2005).…”