 Ralph, The First Cloned Rat
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Sept. 26, 2003 — French researchers have cloned rats, a first for the species which is important in research on human diseases including diabetes and hypertension, Thursday's issue of the review Science said.
The rat had not been cloned earlier due to the fact that almost all oocytes — a cell from which an egg or ovum develops by meiosis — "spontaneously, though abortively, activate within 60 minutes of their removal from oviducts," the authors explained.
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They were able to overcome the problem with a "one-step SCNT procedure for the rapid substitution of the endogenous meiotic metaphase by an exogenous mitotic one" using MG132, a protease inhibitor to stabilize the oocyte.
With this method, researchers were able to implant 129 cloned embryos in two females; one became pregnant and gave birth to three male rats. One of those died shortly after birth but two "developed normally into sexually mature animals."
"We have also obtained normal progenies (size, weight and development) from two additional cloned female rats, demonstrating the potential of the technique for the development of fertile rat lines of both sexes," the researchers added.
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