- Obtaining, for the first time, live-born rabbits derived from the third generation of serially cloned, nuclear transfer, 8-cell embryos [Piotrowska et al., 2000 – Biology of Reproduction 63, 677-682] (Photo 2).
- Obtaining, for the first time, live-born mice after transfer of 8-cell embryonic nuclei into enucleated zygotes. Zygotes were enucleated using the original method developed at the Department (selective enucleation) in which only the pronuclear envelope is removed leaving in the cytoplasm liquid pronuclear contents and nucleoli. Selectively enucleated GV oocytes reconstituted with 2-cell blastomere nuclei can develop in the presence of follicular cells, at least up to the blastocyst stage. These studies revealed the importance of nucleolar material in proper formation of nuclei in reconstituted oocytes and developing embryos [Gręda et al., 2006 - Reproduction 132, 741-748]
- Obtaining, for the first time, the full preimplantation development (23% of blastocysts) after transfer of embryonic nuclei into selectively enucleated immature [germinal vesicle (GV) stage] mouse oocytes. It was shown that the presence of surrounding follicular cells during in vitro maturation of selectively enucleated GV oocytes reconstituted with embryonic nuclei is a sine qua non condition of their further successful development. These studies revealed also the importance of nucleolar material in proper formation of nuclei in reconstituted oocytes and developing embryos [Mohammed et al., 2008 – Molecular Reproduction and Development 75, 1269-1280].
- Obtaining, for the first time, embryonic-somatic chimaeras in the mouse and sheep after microsurgical transfer of foetal fibroblasts into cleaving embryos. It was shown that in mouse, some of the introduced somatic cells underwent fusion with host cells and survived (as hybrid cells) in tissues derived from all three germ layers [Piliszek et al., 2007 – Reproduction 133, 207-218]. Further analysis of molecular markers of pluripotency in preimplantation chimaeric embryos proved that introduced cells undergo reprogramming in the early embryo environment. The presence of the introduced somatic cells was also confirmed in several tissues of born chimaeric lambs using RAPD method [Karasiewicz et al., 2008 - International Journal of Developmental Biology 52, 315‑322].
- Development of highly efficient method of vitrification of bovine oocytes and early embryos [Papis et al., 2000 – Theriogenology 54, 651-658]. This method was patented in Japan in 2000 (patent no. 2044323).
- Showing that the supplementation of culture media with melatonin has beneficial effect on in vitro development of bovine embryos [Papis et al., 2007 – Journal of Pineal Research 43, 321-326].
- Obtaining full preimplantation development of selectively enucleated bovine zygotes reconstituted with aurochs (Bison bonasus bonasus) skin fibroblasts nuclei [Modliński et al., 2008 – in “Od genomu tura po ksenotransplantacje “ (From the aurochs genome to xenotransplantations) OWN Poznań 9-29; Loi, Modliński, Ptak 2011 – Theriogenology 78, 211-228] (Photo 5).
Indicating, for the first time, that it is possible to induce the embryonic diapause (ED) in blastosycyst of non-diapausing mammalian species and that such induction is fully reversible. Lambs were born from ovine blastocysts in which the ED was experimentally induced. It implies that ED is phylogenetically conserved phenomenon and not secondarily acquired by embryos and questions the current model of independent evolution of ED in different mammalian orders. Therefore, it provides a starting point to verify the flexible occurrence of ED in mammals and opens new perspectives for reproductive and evolutionary biology. If diapause does occur in all mammals (as we postulate), this may have huge implications for human pregnancy