Cleavage of rabbit eggs after microsurgical injection of testicular spermatozoa

A rabbit testicular spermatozoon or sperm head was injected microsurgically into the cytoplasm of each of 64 mature rabbit oocytes and 71 control eggs were pricked similarly but without sperm injection. A significant proportion of injected eggs developed pronuclei by 9 h and 19 had undergone regular cleavage to two cells and two to three cells by 20-23 h. By contrast, only two of 71 control eggs had cleaved at that time, the others having fragmented or remained at the 1-cell stage. No pregnancies were obtained after surgical transfer of the cleaved injected eggs to the oviducts of synchronized recipients. The results nevertheless provide some preliminary support for efforts to obtain live young with testicular sperm nuclei.