Intracytoplasmic injection of porcine, bovine, mouse, or human spermatozoon into porcine oocytes

We determined the incidence of activation, male pronuclear formation, and a pposition of pronuclei in porcine oocytes following intracytoplasmic inject ion of various porcine sperm components and foreign species spermatozoa, su ch as that of cattle, mouse or human. The porcine oocytes were activated by injection of a spermatozoon or an isolated sperm head. In contrast, inject ion of either sperm tail or a trypsin- or NaOH-treated sperm head failed to induce oocyte activation. Because injection of mouse, bovine, or human spe rmatozoon activated porcine oocytes, the sperm-borne activation factor(s) i s not strictly species-specific. Male pronuclear formation and pronuclear a pposition were observed in porcine oocytes following injection Df porcine, bovine, mouse or human spermatozoa. Electrical stimulation following sperm cell injection did not enhance the incidence of male pronuclear formation o r pronuclear apposition compared with sperm cell injection alone (P > 0.1). Following porcine sperm injection, the microtubular aster was organized fr om the neck of the spermatozoon, and filled the whole cytoplasm. In contras t, following injection of bovine, mouse, or human spermatozoon, the materna l-derived microtubules were organized from the cortex to the center of the oocytes, which seems to move both pronuclei to the center of oocytes. Cleav age to the two-cell stage was observed at 19-21 hr after injection of porci ne spermatozoon. However, none of the oocytes following injection of mouse, bovine, or human spermatozoa developed to the mitotic metaphase or the two -cell stage. These results suggested that the oocyte activating factor(s) i s present in the perinuclear material and that it is not species-specific f or the porcine oocyte. Self-organized microtubules seemed to move the pronu clei into center of oocytes when foreign species spermatozoa were injected into porcine oocytes. (C) 1999 Wiley Liss, Inc.