The introduction of different micromanipulation techniques into reproductive and developmental biology has helped us not only to answer many essential biological questions but it is now evident that these techniques also have wide practical applications. In human-assisted reproduction, the most commonly used approach is the injection of a donor sperm into the oocyte cytoplasm--intracytoplasmic sperm injection. It is, however, speculated that with these techniques it would be also possible to improve the oocyte developmental potential especially in those cases when the quality of the cytoplasm is rather poor and thus its function is compromised. Another important application would be the elimination of mutated mitochondrial DNA (mtDNA) by transferring the nuclear material from an abnormal oocyte into a healthy donor oocyte cytoplast. Some of these techniques were already successfully tested in experimental animals, but it is evident that before their introduction into human medicine many questions must be answered, and we must be sure that these approaches are absolutely or almost absolutely safe. In our contribution, we will be specifically oriented to the nuclear (nuclear material) replacement approaches that could be potentially used to prevent the transmission of mutated mtDNA from mother to offspring. Because these techniques are very delicate, some training with oocytes from other species other than human is strongly recommended. 2007, Elsevier Inc.

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