In vitro cultivation of mammalian embryos.

The cultivation part of in vitro production of embryos has been summarized. The aim of cultivation is to provide the necessary environmental conditions for the further development of fertilized embryos. In optimal cases, the embryos pass the developmental block at different stages in each species and develop into viable morula or blastocyst stage embryos. One of the cultivation methods is to transfer the zygote obtained by in vitro fertilization into the oviduct of a mammal. Their development is ensured such a way and the morula or blastocyte stage embryos are recovered by flushing. Another possibility is the co-cultivation: the embryos develop in a cultivation medium in the presence of helper cells. These can originate from the tissues of the reproductive organ, however several other cells can also be used (liver, kidney). These ensure the favourable environment for the embryos partly through their metabolic products partly through the detoxification effect. The culture medium is supplemented by amino acids, proteins, vitamins and different hormones. The presence of helper cells, as well as the supplementation of culture medium by blood serum or serum albumin mean that not completely known materials of animal origin can also be found in the in vitro system. These may also contain infectious agents and their varying composition can make the results uncertain making the reproductibility of the individual experiments difficult. For this reason simple, chemically well defined cultivation systems have also been elaborated. In this case the biological materials necessary for the embryos have been substituted by synthetic compounds. Literature of the embryo cultivation has also been reviewed pointing out the tendency of development of cultivation systems.