The stages at which human fertilization arrests: microtubule and chromosome configurations in inseminated oocytes which failed to complete fertilization and development in humans.

The goal of fertilization is the union of one, and only one, sperm nucleus with the female pronucleus within the activated oocyte. For this to occur successfully, several events must transpire, including the incorporation of the entire spermatozoon into the oocyte, the completion of meiotic maturation with the extrusion of the second polar body, the metabolic activation of the previously quiescent oocyte, the decondensation of the sperm nucleus and the maternal chromosomes into the male and female pronuclei respectively, and the cytoplasmic migrations of the pronuclei, which bring them into apposition. Defects in any of these events are lethal to the zygote and might prove to be causes of infertility. In this study, the microtubules and DNA were imaged in inseminated human oocytes that had been discarded as unfertilized. The presence and number of incorporated sperm tails were also documented using a monoclonal antibody specific for the post-translationally modified acetylated-alpha-tubulin found in the tail, but not the oocyte, microtubules. An analysis of 211 oocytes from failed in-vitro fertilizations from 58 patient couples resulted in the determination of several previously undetectable phases at which fertilization arrests: (i) metaphase II arrest; (ii) arrest after the successful incorporation of the spermatozoon, (iii) arrest after the formation of the sperm aster; (iv) arrest during mitotic cell cycle progression; and (v) arrest during meiotic cell cycle progression. Data on polyspermy and arrested embryonic development are also presented. These results have implications for the diagnosis and treatment of female, as well as male, infertility.(ABSTRACT TRUNCATED AT 250 WORDS)