Word: nuclei
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...John Gearhart of Johns Hopkins -? one of the authors of a successful study released last week in which stem cells were created from dead human embryos. ACT's experiment is raising eyebrows because cows and humans took separate evolutionary paths more than 10 million years ago; the two cell nuclei are so different that they're unlikely to stick together for long. "There's no reason to believe this thing would get past a few cell divisions," says Elmer-DeWitt...
...example, obtain healthy cells from a patient with leukemia or a burn victim and then transfer the nucleus of each cell into an unfertilized egg from which the nucleus has been removed. Coddled in culture dishes, these embryonic clones--each genetically identical to the patient from which the nuclei came--would begin to divide...
...women, and suspect that the fault lies not in the chromosomes but in the biological machinery that controls cell division. To test this idea, Dr. Jamie Grifo, director of reproductive endocrinology at New York University Medical Center, and his colleague, Dr. John Zhang, have microsurgically transplanted the chromosome-containing nuclei from older women's eggs into younger women's eggs from which the nuclei have been removed. The transplants took, and while 40% to 50% of older eggs show chromosomal abnormalities, says Grifo, "the rate was only 15% with the transplants...
...portfolio, it is no wonder these mood-changing brain chemicals have been implicated in so many mental disorders. And it is not surprising that serotonin appears to be especially important--the first among equals, in a sense. The nerve cells that specialize in serotonin production originate in the raphe nuclei, in a region right atop the spine that nimh's Hyman calls "the deep basement of the brain." From there, these neurons extend vinelike projections called axons up through the brain and down into the spinal column. The axons form a sort of neurological interstate-highway network, over which serotonin...
Another line of investigation revealed that serotonin may play a role in sleep. Destroy the raphe nuclei in cats, and they develop permanent and total insomnia. Give the wakeful cats a shot of serotonin, and they immediately go to sleep. In humans the amino acid L-tryptophan, which is converted to serotonin in the brain, is sometimes used as a sleeping pill. (A bad batch of L-tryptophan killed several people in the late 1980s and effectively killed the craze.) In another experiment, researchers discovered that when they stimulated raphe cells to release extra serotonin not in the brain...