ROUND SPERMATID TRANSFER AND EMBRYO DEVELOPMENT

With the advent of assisted reproductive technology, pregnancy has bec ome possible without sperm. The nucleus of the round spermatid, which contains a complete haploid set of chromosomes, can be used as a subst itute for spermatozoa in animals and humans. In the mouse, round sperm atids from surgically induced cryptorchid and prepubertal testes can f ertilize normally and develop into normal offspring. The spermatid nuc leus develops into a large pronucleus only when the oocyte is activate d by artificial means, such as electrostimulation and oscillogen injec tion. Nuclei of mouse primary spermatocyte have been injected into ooc ytes and found to undergo meiosis, form an embryo and produce live you ng. Intracytoplasmic injection of male immature germ cells may become available as a treatment for patients with azoospermia due to maturati on arrest.