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This Article Full Text Full Text (PDF) All Versions of this Article: 70/1/46    most recent biolreprod.103.018200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Choi, Y.-H. Articles by Hinrichs, K. Search for Related Content PubMed PubMed Citation Articles by Choi, Y.-H. Articles by Hinrichs, K. Agricola Articles by Choi, Y.-H. Articles by Hinrichs, K.

Activation of Equine Nuclear Transfer Oocytes: Methods and Timing of Treatment in Relation to Nuclear Remodeling¹

Departments of Veterinary Physiology and Pharmacology³ Large Animal Medicine and Surgery,⁴ College of Veterinary Medicine, Texas A&M University, College Station, Texas 77843-4466

Early development of embryos produced by transfer of equine nuclei to bovine cytoplasts is superior to that of intraspecies equine nuclear transfer embryos. This may be related to differences in chromatin remodeling or efficiency of activation between the two oocyte types. The pattern of donor nucleus remodeling was examined in equine-equine and equine-bovine reconstructed oocytes. Chromosome condensation occurred in equine cytoplasts by 2 h but was not seen in bovine cytoplasts until 4 h. We investigated the effect of activation of equine-equine reconstructed oocytes at <30 min or at 2 h after reconstruction. Four activation treatments were evaluated at each time point: injection of sperm extract alone, or in combination with 6-dimethylaminopurine (6-DMAP), cytochalasin B, or 1% dimethylsulphoxide. There was no significant difference in normal cleavage rate or average nucleus number of embryos between equine oocytes activated <30 min or at 2 h after reconstruction. The combination of 6-DMAP with sperm extract significantly (P < 0.01) improved cleavage rate compared with the other three treatments. Activation with sperm extract and 6-DMAP 2 h after donor nucleus injection gave the highest cleavage (79%) and the highest cleavage with normal nuclei (40%). Sperm extract and 6-DMAP also effectively activated oocytes parthenogenetically, yielding 83% cleavage and 73% cleavage with normal nuclei. These results indicate that although nuclear remodeling occurs rapidly in equine cytoplasts, early activation does not improve embryonic development after reconstruction.

¹ Supported by the Bio-Arts Research Corporation and the Link Equine Research Endowment Fund (Texas A&M University).

² Correspondence: Katrin Hinrichs, Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4466. FAX: 979 845 6544; khinrichs{at}cvm.tamu.edu

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