Cytogenetic study of parthenogenetically activated XXXX oocytes matured in vivo and in vitro.

@entity95 @entity291 @entity7978
Three experiments were performed to evaluate the potential for parthenogenetic activation of @entity291 oocytes in in vitro fertilization systems and to determine the chromosome complement of the resulting parthenogenotes. In the first experiment, immature oocytes from slaughtered @entity291 were matured in vitro in @entity7978 ( @entity7978 ) for 24 h to simulate in vitro fertilization conditions. Subsequently, a portion was fixed, and the remainder were transferred to @entity95 oviducts. Oocytes were then cultured for 6-8 h or for 24 h with Colcemid present during the last 6 to 8 h and fixed on slides and examined. In the second experiment, mature oocytes were collected from the preovulatory follicles, and the oocytes were subjected to the same culture as in experiment I. In the third experiment, oocytes were treated as in experiment II, except that instead of transfer to @entity95 oviducts, they were cultured an additional 48 h in vitro. In experiment I, 131 oocytes were fixed after culture in @entity7978 . Of the 79 oocytes analyzed in the pre- @entity95 group, 71 (90%) were at the second meiotic metaphase (MII), and 8 (10%) were at pre-MII stage; none were activated. After transfer to @entity95 , 291 were fixed. Of these, 80 were analyzed; 37 (46.3%) were MII, 7 (8.6%) were pre-MII, and 36 (45%) were activated. Of the 36 activated oocytes, 26 (72.2%) were haploid, 4 (11.1%) were diploid, 1 (12.8%) was tetraploid, and 5 (13.8%) were in the process of endoreduplication. In experiment II, 51 oocytes were fixed after culture in @entity7978 of which 36 (70.6%) could be analyzed; 30 (83.3%) were MII, and 6 (16.7%) were pre-MII. After culture in the @entity95 , 68 were fixed of which 27 (39.7%) could be analyzed. Of these 27, 20 (74.1%) were MII, and 7 (25.9%) were activated; 6 were haploid, and 1 was endoreduplicating. In experiment III, 30 oocytes were fixed at the end of the culture period; only 10 could be analyzed of which 8 (80%) were MII and 2 (20%) were pre-MII. In all, 46% of in vitro and 26% of in vivo matured oocytes were activated, based on chromosomal analysis. Of those activated, the majority (74.4%) were haploid, suggesting that activation occurs at or after completion of MII. Endoreduplication appears to be one of the mechanisms leading to the formation of diploid and polyploid parthenogenotes.
