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hi all i just love to hear about brain cells regenerating themselves. janet -------------------------------------------------------------------------- New experiments bring hope for brain-spinal cord regrowth -------------------------------------------------------------------------- Copyright _ 1996 Nando.net Copyright _ 1996 The Associated Press (Sep 17, 1996 01:01 a.m. EDT) The human brain created Shakespeare's plays, Darwin's theory of evolution and the Great Pyramids. But though it's the most impressive chunk of flesh on the planet, the human brain can't do something that the goldfish brain can -- regenerate its damaged cells. Now, new experiments by Israeli researchers have pointed to a strategy that doctors might one day use to reverse that inability, which one researcher theorizes is the legacy of an ancient evolutionary compromise that traded repairability for brainpower. "If you're Christopher Reeve, you'd really like to know this," said professor G. Miller Jonakait of Rutgers University in Newark, N.J., who was not involved in the research. Lead researcher Michal Schwartz, a professor at the Weizmann Institute of Science in Rehovot, Israel, said it's difficult to speculate "whether it will be easy or difficult to translate it into humans beings, but definitely it is applicable." The central nervous system, which includes the brain and the spinal cord, has erected a biochemical barrier against the agents that repair damaged cells. So any central nervous system damage, such as the paralysis caused by a severed spinal cord or the various defects that can be caused by a brain lesion, is more or less irreversible. But research by Schwartz and several colleagues suggests a way to do an end-run around the brain's repair barrier. If doctors could get past the barrier, people with some types of brain damage might regain their cognitive abilities and paralyzed people might walk again. The results are reported in the September issue of the FASEB Journal, a publication of the Federation of American Societies for Experimental Biology. The Israeli researchers studied macrophages, cells that rally the immune system to repair wounds. Most of the body's cells, including nerve cells outside the central nervous system, respond to macrophages. But cells in the brain and spinal cord don't. "Here is this important cell type that's so important everywhere else in the body for recovery after injury and the brain inhibits it," Jonakait said. Myelin, a protein that sheaths nerve fibers in the brain and spinal cord, prevents macrophages in the brain from doing their work. But the Israeli researchers found that if macrophages are activated in another part of the body and then transplanted into the central nervous system, they do their job quite effectively. "This is the breakthrough of this work, the recruitment and adequate activation of macrophages," Schwartz said. She and her colleagues incubated rat macrophages with sciatic nerve cells, which are located in the hip and are able to regenerate. Then they transplanted the macrophages into the optic nerves of the same rats the cells had been taken out of. Optic nerves can't normally regenerate, but the ones in the treated rats did. Schwartz said they are now trying to see if the rats actually can recover the use of their optic nerves in addition to regrowing them, and thus regain their sight. They're also doing the same experiment to see if it works on rats with damaged spinal cords. It's a long way from experiments in rats to a therapy for people. But pharmaceutical companies have expressed interest in macrophages, Jonakait said. She envisions therapies that exploit macrophages being useful in a matter of years. Schwartz theorizes that the brain's inability to regenerate may have stemmed from an evolutionary tradeoff: Somewhere between amphibians and mammals the brain became inaccessible to macrophages and other tools of the immune system. That kept the immune system from killing brain cells and thus molding the brain in undesirable ways. In a brain accessible to the immune system, memories could be wiped out and important structures destroyed as a by- product of the body's effort to fight foreign invaders. "This benefit becomes a drawback once there is injury," Schwartz said. "The tradeoff is the loss of the ability to regenerate." -------------------------------------------------------------------------- [log in to unmask]