ACT researchers successfully repeat human embryo cloning experiment.The only researchers to publicly prove they have cloned a human embryo said they have successfully repeated the experiment, growing an embryo to the 16-cell stage. Researchers at Advanced Cell Technology of Worcester, MA have also repeatedly created embryos using a process called parthenogenesis parthenogenesis (pär'thənōjĕn`əsĭs) [Gr.,=virgin birth], in biology, a form of reproduction in which the ovum develops into a new individual without fertilization. , which uses only a human egg cell-no sperm or cloning required. The company said the experiments, reported in the January issue of Wired magazine, are not breakthroughs but a natural progression of its efforts to create human embryonic stem cells Embryonic stem cells (ES cells) are stem cells derived from the inner cell mass of an early stage embryo known as a blastocyst. Human embryos reach the blastocyst stage 4-5 days post fertilization, at which time they consist of 50-150 cells. ES cells are pluripotent. for medical therapy. Sheep, cattle and pigs have all been cloned using an egg cell and an adult somatic somatic /so·mat·ic/ (so-mat´ik) 1. pertaining to or characteristic of the soma or body. 2. pertaining to the body wall in contrast to the viscera. so·mat·ic adj. (body) cell from another animal. But critics had questioned whether the cloning process known as nuclear transfer has ever worked with humans. ACT medical director Robert Lanza Robert Lanza is is Chief Scientific Officer Advanced Cell Technology (ACT) and Adjunct Professor at the Institute for Regenerative Medicine, Wake Forest University School of Medicine [1]. Lanza received both BA and MD degrees from the University of Pennsylvania. , MD said the new experiments, which began last June, suggest they were successful. Even more successful were the parthenogenesis experiments, in which 5 of 8 human eggs were coaxed to grow into blastocysts. At this stage-approximately 100 cells-stem cells can be harvested and used to grow any type of body cell or tissue. Scientists hope the cells may one day allow the creation of custom-made tissue transplants. Opponents contend that the cloning technology involved in making embryonic stem cells creates a living human being. Lanza said parthenogenesis bypasses these objections, as it does not appear to lead to the development of a fetus in mammals. Yet the resulting blastocyst blastocyst /blas·to·cyst/ (-sist) the mammalian conceptus in the postmorula stage, consisting of an embryoblast (inner cell mass) and a thin trophoblast layer enclosing a blastocyst cavity. , called a parthenote, can be a source of embryonic stem cells. Tissues from such cells would be easier to match with patients and less likely to be rejected, Lanza said, because they contain the DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. of only 1 person. They also would be more readily available than tissue from a patient's cloned cells, which require months to prepare. Just 40 batches, or lines, of parthenote-generated stem cells stem cells, unspecialized human or animal cells that can produce mature specialized body cells and at the same time replicate themselves. Embryonic stem cells are derived from a blastocyst (the blastula typical of placental mammals; see embryo), which is very young could create tissue matches for 70% of the US public, Lanza said. And because embryonic stem cells are immortal, it would not take many human eggs to create several dozen stem cell lines. |
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