Editor's note: Science Scan is a roundup of recently published biotechnology-related research:
A little like wrapping waterproof tape around a damaged garden hose, a just-reported transplant therapy sheaths injured spinal cord neurons in a protective sleeve of restorative cells.
Last week in Los Angeles, neuroscientists at Yale University and Alexion Pharmaceuticals Inc., both in New Haven, Conn., reported to the 28th annual meeting of the Society for Neuroscience on "Facilitation of axonal conductance across transected rat spinal cord following transplantation of olfactory ensheathing cells or Schwann cells."
The transplanted porcine cells wrapped around the damaged spinal-cord neurons, and showed restoration of normal nerve signal conduction. Apparently they acted by restoring the myelin coating, which resembles insulation, around the axons.
"We are encouraged by Alexion's results," commented Augusto Odon, president of the Myelin Project, in Washington. "Studies performed by Myelin Project researchers on both sides of the Atlantic," he said, "have shown that these cells not only promote axonal regrowth, but also foster remyelination of naked axons." He suggested that this "may thus greatly contribute to ongoing efforts to remyelinate the central nervous systems of multiple sclerosis and leukodystrophy sufferers."
Yale neurologist Jeffery Kocsis, a co-author of the poster, said his laboratory and that of Alexion's William Fodor, have "started to test these cells in primates, and are encouraged by preliminary results obtained from transgenic pig cells that look similar to the results we obtained in rats." Fodor is senior director of xenotransplantation at Alexion.
He cited statistics from the Christopher Reeve Foundation that more than half of all non-fatal spinal cord injuries in the U.S. are suffered by individuals between the ages of 16 and 30, of whom 90 percent spend the rest of their lives severely disabled. Alexion's president and CEO, Leonard Bell, said, "We look forward to the day when we will be able to provide a ready source of cells with the potential to restore function to patients suffering from paralysis due to spinal cord injury."
Lowly Laboratory Weed Has Same Neurotransmitter Receptor As Matching Molecule In Human Brain
What mice are to research biologists, the mouse-ear cress is to laboratory botanists. This modest weedy plant is better known in those plant-oriented scientific circles as Arabidopsis thaliana. Now, that weed looks apt for taking on chores, such as drug screening, usually assigned to mouse models.
A paper in this week's Nature, dated Nov. 12, 1998, bears the noncommittal title "Glutamate receptor genes in plants." Its senior author is yeast geneticist Gloria Coruzzi, a biology professor at New York University. Her article reports that A. thaliana uses one of the same communication systems as does the human brain.
Browsing through the plant's genome, she and her co-authors turned up the gene sequence for glutamate receptors. In human brains, the amino acid glutamate is a multipurpose neurotransmitter, involved in everything from memory acquisition and storage to neurological ailments, such as schizophrenia and Alzheimer's disease. Its receptors triage the passage in nerve cells of only certain molecules.
Finding the glutamate receptor in A. thaliana, said Coruzzi, "opens up a new connection between plants and animals."
Of course, glutamate is not the only plant substance that functions in the human brain. Others include caffeine and cocaine, to name just a very few. Until now, it was generally believed that the receptors for these transmitter molecules exist only in animals. No longer, according to the Nature paper.
Several years ago, Coruzzi noted that the weed's uptake of nitrogen from the atmosphere into glutamate was activated by light. She suspected that A. thaliana might possess a light-sensing receptor for the neurotransmitter.
She and her co-authors hunted for a gene sequence in the plant similar to the human glutamate receptor sequence, and found it. What's more, it worked in Arabidopsis cells the same way as their counterparts in human brain cells. When her team blocked the plant's glutamate receptor, it grew much longer stems, and made much less chlorophyll. This implied that inactivating those glutamate receptors blocked the weed's ability to absorb light.
"These results illustrate," Coruzzi said, "that the plants possess a signaling system for 'brain' chemicals, which could enable researchers to use Arabidopsis as a model system for studying how glutamate and its chemical cousins work inside the cell. What's more, the findings provide an interesting clue to evolutionary biologists about plant-produced neurotoxins."
She concluded that scientists "might be able to use these plants as a screen for new drugs. Growing Arabidopsis in the presence of candidate compounds, and simply keeping an eye out for longer stem growth, may be a cost-effective first pass at sifting through thousands of potentially useful therapeutic compounds."
Prostate Cancer Gene Found On X Chromosome
Despite the fact that prostate cancer accounts for more than 35 percent of all neoplasms affecting men, our understanding of the molecular determinants of prostate cancer susceptibility remains "rudimentary."
This observation appears in an article titled "Evidence for a prostate cancer susceptibility locus on the X chromosome," in the October 1998 issue of Nature Genetics. Its 41 co-authors conducted a massive DNA-linkage analysis of 360 prostate-affected families at four major urological centers, two in the U.S., one each in Finland and Sweden.
In that extended pedigree, the teams canvassed 1,989 family members, of whom 1,568 had the disease. Of this number, they DNA-typed 1,020 and tracked the disease gene region to the long arm of chromosome X.
The consortium's suspicion focussed on the sex-linked X chromosome, because of "a statistically significant excess risk of prostate cancer in men with affected brothers, as compared with those with affected fathers." This pattern, they pointed out, "was "consistent with the hypothesis of an X-linked, or recessive, model of inheritance."
"Genetic mapping of the locus," according to the paper, "represents an important initial step in the identification of an X-linked gene implicated in the etiology of hereditary prostate cancer." It noted that over 200,000 new prostate cancer cases are diagnosed in the U.S. each year, and that 40,000 deaths stem from the disease annually . n