Bioscientifica Proceedings

The resting pool of primordial follicles in mammalian ovaries is a potential resource for the genetic manipulation of domestic animals, the preservation of endangered species, and the amelioration of some forms of infertility in humans. Exploitation of this large reservoir of follicles depends on the development of methods for activating primordial follicles to begin growth in vitro and of methods for sustaining follicular growth to the stage at which oocytes are capa...

The ability to mature, be fertilized and finally to develop into a viable embryo is acquired gradually by the oocyte during progressive differentiation throughout folliculogenesis. This process starts with oocyte growth during the first steps of follicular development. As the oocyte is close to its final size, other modifications occur, less spectacular but at least as important in determining the resulting ability of the oocyte to accomplish its reproductive purpose (developm...

The mammalian embryo undergoes considerable changes in its physiology and energy metabolism as it proceeds from the zygote to the blastocyst stage. Complete development of the mammalian zygote in vitro was restricted to a few strains of mice and their F1 hybrids for many years, as the ruminant embryo arrested development at the 8- to 16-cell stage. The introduction of co-culture of ruminant embryos with somatic cells in the mid-1980s helped to alleviate this in vi...

Methods for sexing preimplantation embryos range from karyotyping to recording speed of development in vitro. The only method used routinely on a commercial scale is to biopsy embryos and amplify Y-chromosome-specific DNA using the polymerase chain reaction. This method is effective for more than 90% of embryos and is >95% accurate. Within males, spermatozoa are essentially identical phenotypically due to: (1) connection of spermatogenic cells by intercell...

The reconstruction of mammalian embryos by transfer of a blastomere nucleus to an enucleated oocyte or zygote allows for the production of genetically identical individuals. This has advantages for research (that is, as biological controls) and commercial applications (that is, multiplication of genetically valuable livestock). However, the number of offspring that can be produced from a single embryo is limited both by the number of blastomeres (embryos at the 32–64-cell...