I'm about to see something odd. I'm about to see the creation of a sheep with a partly human liver.
But first things first: why would anyone want to put human cells into a sheep?"Yes. Stem cells from an adult," says the assistant. He positions the needle so that the fluid will be injected into the belly of the fetus, and pushes the plunger.Once the fire spread beyond the maintenance room, it continued along newly refinished lanes and toward the front of the building and lounge area. Firefighters responding to the fire at 2:39 a.m. initially tried an interior attack, but as the rear of the building became unstable they pulled back and fought the fire defensively. Valued at $1,500,000 with contents of $500,000 the building was a total loss."No. Although as much as 15 percent of the sheep may be cells of human origin, in all outward respects, these are normal sheep.""And at that stage, part of its liver will be human?" "Yes. The cells we injected will migrate through the fetus's body and settle into different organs. Once the cells have settled in an organ, they start to divide. The cells around them tell them what tissue to become--so the human cells that arrive in the liver will become liver cells. Over time, as the cells keep dividing, you get clumps of human cells--so parts of the liver are purely human."3M, Scotch, Post-it, Scotchgard, Thinsulate, Scotch-Brite, Filtrete, Command and Vikuiti are trademarks of 3M. Other trademarks or names may be the property of their owners.1) Iron Man, which monitors circuit boards that can be damaged by improperly grounded soldering irons, tweezers and similar hand tools;For more information, visit http://www.3m.com/electronics.> About 3M ElectronicsBut even if no organ is ever transplanted to a person from a sheep, the sheep that carry the human cells are fascinating in themselves. There are two reasons why.I wrinkle my nose. "Strong smell of burning flesh," I say.About 3M - A Global, Diversified Technology Company4) Ground Man Plus, which adds monitoring of the operator's wrist strap.3M Electronics is a leading supplier of innovative solutions to the electronics market. 3M's wide array of advanced technologies enable the company to design specialized products intended to help electronics manufacturers improve quality, reduce costs and lower emissions. The company's products help their customers connect, clean, polish, adhere, protect, transport and finish their products. 3M serves customers in numerous market segments, including semiconductor; OEM electronics; computers and peripherals; mobile and hand-held; as well as consumer, aerospace, military, automotive and medical markets.Well, up to a point. But the burning seals the blood vessels shut, so there is no bleeding. None at all.The fetal sheep doesn't reject the human stem cells, however, because the animal hasn't yet developed an immune system of its own. By the time its immune system does develop, it treats the implanted human cells as belonging there, recognizing that they were there to begin with. In principle, then, stem cells from your own bone marrow could be harvested and injected into a fetal sheep. Once inside the sheep, your stem cells would grow and develop into the organ you needed. The new organ could then be transplanted into you. And because it would be genetically identical to your own tissue, your immune system should not reject it.In any case, I think tissue engineers will be able to grow human organs in vats long before surgeons are ready to collect them from sheep. Tissue engineering, which involves coaxing stem cells to become various kinds of tissue, is advancing fast. Already, biologists at the University of Newcastle, in England, have grown a small cube of human liver tissue from stem cells collected from an umbilical cord; another group of investigators has just grown a heart valve. And in the United States, several people have received transplants of new bladders, grown from small pieces of their old ones.The reason rejection happens is easy to understand. The immune system's job is to protect the body from intruders. Transplanted organs, unless they come from someone genetically identical to you, have all the hallmarks of an intruder. And the greater the genetic differences between donor and recipient, the more rapid and violent the immune response. That is why the few attempts to transplant animal organs, such as hearts, into people have been disastrous: the human immune system attacks the organ, quickly killing the alien tissue.And indeed they are. On seeing some of them, I have no idea they are in any way remarkable. They are woolly, they say baaa, they look sheepish. Yet the more I think about it, the more remarkable they seem."Just smells of roast," says the surgeon.3) Ground Man, which monitors process tools in the electronic manufacturing and semiconductor environments; and2) Iron Man Plus, which adds monitoring of the worker's wrist strap and mat;Each stem cell has the potential to become one of many kinds of tissue--which is why stem cells have become such a hot area of research. As stem cells differentiate into tissue of a particular type--heart, say--they switch off the genes they don't need for the heart and switch on the ones they do need. Thus a stem cell would take on such traits of a heart cell as shape and size. Once a cell has committed to a certain path, it loses its flexibility: a heart cell cannot suddenly become a liver cell. Stem cells, then, are cells without commitments.The idea behind the research--which is the brainchild of Esmail D. Zanjani, a professor and chair of the university's department of animal biotechnology--is that one day, perhaps, livers grown this way could be transplanted into people. At present there aren't enough organs available for transplant, so people in need often die while waiting for one. And even if you get the organ you need, your immune system may still reject it soon after the transplant--or years later.The Ground Man monitors have three channels for monitoring metal grounding within process tools, such as pick-and-place machines. If a channel detects a grounding failure, a red alarm appears. Operators have the option of also setting an audio alarm."What happens now?"
But even if no organ is ever transplanted to a person from a sheep, the sheep that carry the human cells are fascinating in themselves. There are two reasons why.
Author: Olivia Judson
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