CRYOPRESERVATION OF MAMMALIAN EMBRYOS AND OOCYTES - RECENT ADVANCES

The cryopreservation of embryos of most domestic species has become a routine procedure in embryo transfer, and recently, advances have been made in the cold storage of mammalian oocytes. The ability to sustain viable oocytes and embryos from mammalian species at low temperature for prolonged periods of time has important implications to basic and applied biotechnology. Recent advances in the study of physico-chemica l behaviour of different cryoprotectants, use of various macromolecule additives in cryoprotective solutions and isolation and use of protei ns of plant and animal origin with antifreeze activity offers many new options for cryopreservation of oocytes and embryos of animal and hum an origin. At the same time rapidly developing methods of oocyte/embry o manipulation such as in vitro embryo production, embryo splitting, e mbryo biopsing for gene and sex determination, embryo cloning and the isolation of individual blastomers, create new challanges in cryoprese rvation. Very recent advances in the cryopreservation of mammalian ooc ytes, in vivo- and in vitro-derived embryos, and micromanipulated embr yos are reviewed in this manuscript.