Culture media for postimplantation embryos

The search for an effective culture medium for postimplantation mammalian embryos is considered from two viewpoints: identification of the medium that gives the best development in culture and of the problems associated with formulating a fully defined medium for such embryos. The types of media that have been applied to the culture of mammalian embryos are reviewed and their effectiveness assessed. At present, the media that support the best development of explanted embryos are composed partly or wholly of heat-activated rat serum, prepared by centrifugation of blood immediately after withdrawal from the donor. Experimental approaches to elaborating fully defined media are considered, and progress with identifying the nutrient requirements of postimplantation mammalian embryos in culture is reviewed. Particular attention is given to the use of extensively dialysed serum which, when supplemented with glucose, amino acids, and vitamins, supports good development of midgestation rodent embryos in vitro.