gene expression and activate the newly acquired capability. The woman will now be monitored to see if her brain function improves, stabilizes, or degrades but less rapidly than would otherwise be expected. Only the right brain hemisphere has been treated. The left hemisphere has its own nucleus basalis, which in this case will not be benefited. One other patient is to be treated in one hemisphere only, then, if all goes well, bilateral treatments will be offered. The research effort is being led by Dr. Mark Tuszynski at the University of California, San Diego, which also hosted the surgery. Dr. Hoi Sang U was the neurosurgeon who performed the operation. The work is based on research with aging monkeys, whose atrophied nerve cells were revitalized and restored to function by a similar procedure.
Stem Cells Show Promise for Heart Repair. Three experiments with animals make the prospect of repairing ailing human hearts with stem cells seem tantalizingly near. Stem cells are unspecialized cells that are able to give rise to many different tissues as well as replenish themselves by division. All the experiments used adult stem cells from bone marrow, and in one case human cells, which can survive and function for extended periods in animal hosts. Bone marrow stem cells are mainly used by the body to form blood cells, but an exciting new finding is that they can apparently form a wide variety of other tissues too. Whether there is, in addition, a special stem cell for the formation of heart tissue is unknown. But the use of adult cells bypasses the ethical problem some have expressed over embryonic stem cells, which in their natural setting develop into fetuses and eventually whole human beings. In one experiment functioning heart tissue was apparently created, the first time this had ever been done. Another experiment used human angioblasts, a special type of marrow stem cell, to form blood vessels in mouse hearts. A third experiment used stem cells to strengthen pig hearts. A team led by Dr. Piero Anversa of the New York Medical College in Valhalla and Dr. Donald Orlic of the National Institutes of Health achieved success in creating mouse heart tissue. Marrow cells from a donor mouse were carefully screened to isolate the most primitive stem cells and exclude those that had already progressed toward becoming blood cells. The stem cells were then injected into hearts of mice that had been given heart attacks by tying off an artery, and they produced an amazing revitalization. New heart tissue was formed, consisting of muscle mass and blood vessels with linings. Ventricular performance improved by 40 percent. The new cells produced a special protein typical of heart cells bound by a connective network so as to beat in unison, further evidence that the new tissue was functioning, though more testing is needed to establish this important property beyond doubt. The second experiment, conducted and reported by Dr. Silviu Itescu and colleagues at Columbia University, used a special type of human marrow stem cell they call an angioblast, which, they say, has the specific function of forming fine blood vessels. Isolated for the first time, the angioblasts were injected
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into the blood stream (not hearts) of rats that had again been given heart attacks by tying off an artery. The damaged hearts had regenerated muscle tissue to replace what had been lost, but the new tissue was deficient in blood supply. This effect is also seen in humans who survive heart attacks (as most do, and indeed this mechanism itself is largely responsible). Over time the blood-deficient replacement muscle is likely to degenerate into scar tissue, so that serious heart problems recur. But in the experiment the angioblasts homed in on the damaged hearts and proceeded to develop into fine networks of blood vessels to provide extra metabolic support. That this effect was seen at all is remarkable enough, but that it happened between two species as different as rats and humans seems all but miraculous and perhaps can be taken as a sign that human-to-human cell injections for the same purpose are not far away. The third experiment involved a Maryland-based private company, Osiris Therapeutics, Inc., and was carried out by Dr. Robert Deans. A second type of stem cell known as a mesenchymal cell was used; pigs furnished both the cells and the experimental model. A roughly human-sized pig is large enough that its heart function can be much more accurately measured than in rodents. In this case, the function improved after cells were injected into the region of a heart attack. Deans hopes to begin clinical trials of his technique within a year.
Implantable Artificial Heart Nears Clinical Trials. Based in Danvers, Massachusetts, and also in Einhoven, Netherlands, Abiomed, Inc., has developed an artificial heart that may at last make a worthy substitute for the natural organ. In use, the new battery-powered heart has no physical connections piercing the skin; power to recharge the battery is transmitted through the intact skin, minimizing the risk of infection. Patients can be fully ambulatory and disconnected between recharges. Like the natural variety, the artificial heart consists of two blood pumping chambers, one to supply the lungs, the other, the rest of the body. Each pump can deliver eight liters of blood (2.12 gallons) per minute. The device is about the size of a grapefruit, and is quiet. The pump rate is adjustable depending on the body’s needs, and an internal monitoring system determines when the battery should be recharged. Heart valves are made of a flexible plastic and coated with an anti-clot-forming material, to minimize the risk of strokes that so plagued the Jarvik-7 heart of two decades ago. Clinical trials of the new heart are to start very soon (and may be under way as you read this). Reportedly the FDA, with mixed feelings, has set very high standards Abiomed’s for the device to be approved, but Abiomed artificial heart is confident of its product and very determined to succeed. Let us wish them well!
Desiccate, Estivate, Reanimate. Exposed to drying conditions, our cells usually die within seconds. A new technique, however, has reanimated dried
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