The starting material for de novo isolation of stem cell lines can be either normal 3.5-days post coitum (dpc) expanded blastocysts or "delayed" blastocysts. Delayed blastocysts are usually collected 4-6 days after ovariectomy. For both groups of blastocysts, tissue culture procedures are similar. The only difference is the timing of the first disaggregation, because delayed blastocysts will initially grow more slowly. - [Read De Novo Isolation of Embryonic Stem (ES) Cell Lines from Blastocysts Protocol]
The basis of this procedure is that two specific cell type preparations may be isolated, exposed separately to various compounds over a range of concentrations, and the cytotoxicity of these determined. Parameters deemed indicative of a cytotoxic effect include a reduction in de novo protein synthesis and decreased glucose and fatty acid metabolism. A cytotoxic effect may indicate that a chemical is likely to be nephrotoxic in vivo. - [Read Isolated Rat Glomeruli and Proximal Tubules]