When researchers consider disease model options, cows generally remain in the pasture. But a bovine tuberculosis epidemic in the United Kingdom has made the grazers invaluable, not only for studying ways to stymie Mycobacterium bovis, the bovine version of the tubercle bacilli that causes disease, but the human version, Mycobacterium tuberculosis, as well.

By | June 24, 2002

When researchers consider disease model options, cows generally remain in the pasture. But a bovine tuberculosis epidemic in the United Kingdom has made the grazers invaluable, not only for studying ways to stymie Mycobacterium bovis, the bovine version of the tubercle bacilli that causes disease, but the human version, Mycobacterium tuberculosis, as well. At the Fourth World Congress on Tuberculosis, held recently in Washington, DC, tuberculosis (TB) investigator Glyn Hewinson, Department of Bacterial Diseases, Veterinary Laboratories Agency, UK, expounded on the virtues, and liabilities, of using Bossy the cow as a human TB model. Cow pluses: They exhibit a humanlike pathology and immunological response; researchers have a large array of bovine immunological reagents available; calves are immunocompetent early on; vaccines can be tested in the natural host species; and the United Kingdom's TB epidemic has made clinical material plentiful. Cow minuses: They are relatively expensive to study; few suitable adjuvants exist (helper molecules required to boost a vaccine-stimulated immune response); and investigators, strictly speaking, are working on a different bacterium. However, according to Hewinson, the recently completed sequence of the M. bovis genome, to be published in the next few months, has revealed that M. tuberculosis and M. bovis are very closely related, suggesting that M. bovis vaccines may also be effective against M. tuberculosis.

How rhodopsin gets its groove on

Image: Marlene Viola
By quick-freezing the eye's light receptor (rhodoposin) in its active form (metarhodopsin II), researchers viewed an activated receptor for the first time (G. Choi, "Structural studies of metarhodopsin II, the activated form of the G-protein coupled receptor, rhodopsin", Biochemistry, 41:7318-24, June 11, 2002). Lasting for mere milliseconds, the active phase of a receptor is transient and difficult to observe using conventional techniques such as X-ray crystallography. Already having the structure of the turns and helices that comprise rhodopsin in its inactive form, Philip Yeagle, department head, Molecular and Cell Biology, University of Connecticut, Storrs, says that freezing the receptor allowed them to take measurements of metarhodopsin II. These measurements serve as a manual for assembling the turns and helices. "It's kind of like using pieces of Legos to build a 3-D model," says Yeagle. When light activates the receptor, the second and third cytoplasmic loops change their shape, forming a groove on the receptor's surface. "Now that we see how it binds to the next protein in the sequence, we hope to see how it communicates to proteins further downstream," Yeagle says.

New word in gene-expression lexicon

Image: Erica P. Johnson
Using a high-throughput method dubbed voxelation, researchers from the University of California, Los Angeles, School of Medicine have developed a rapid way of determining where genes misfire in a murine pharmacological model of Parkinson disease (V.M. Brown et al., "Multiplex three-dimensional brain gene expression mapping in a mouse model of Parkinson's disease," Genome Research, 12:868-84, June 2002). To achieve voxelation, a brain is cut into cubes and spatially analyzed with microarrays, producing several volumetric maps of gene expression patterns. Forty voxel images for 9,000 genes were acquired from pharmaclogical models of Parkinson disease in mice. Desmond Smith, assistant professor of pharmacology at UCLA, says that the observed dramatic shifts in gene expression were precisely in the locations predicted. "We were gratified to find our expectations borne out of our data." Smith predicts that voxelation will prove a useful technique in decoding mysteries of many disorders. "To understand how the genome constructs the brain, we have to understand how the building blocks are put into place, and the way to do that is to look at the building being constructed."

A ken and coin for yeast

Image: Erica P. Johnson
Incyte Genomics of Palo Alto, Calif., sparked an outcry from researchers this month when it required academic laboratories and institutions to purchase subscriptions to the newly expanded Yeast Proteome Database (YPD) after more than three years of free access. "We all became addicted to it, because it's an excellent database," says Charles Boone, associate professor of microbiology at the University of Toronto. "And now we're asked to pay what is a fair amount of cash for us." James I. Garrels, formerly at Cold Spring Harbor Laboratory in New York, created YPD at his company Proteome, which Incyte acquired for $77 million (US) in cash and equity in December 2000. Now Incyte charges from $2,000 a year per laboratory to $100,000 for large institutions such as the National Institutes of Health-fees company officials say are reasonable for what is now a six-volume resource. (The Celera Discovery System subscription costs $17,000 a year per user for one to five users.) "It was an across-the-organization decision that it was no longer in our best interests to continue to offer a free database," says Kevin Cannon, Incyte's senior marketing director for genomics. Within the first week, 58 researchers and institutions signed on to the service, Cannon says. But some scientists insist the data should remain free. J. Michael Cherry, who directs the complementary Saccharomyces Genome Database at Stanford University, has already talked with NIH about funding further expansion into proteins and plans to poll researchers' needs during the annual Yeast Genetics and Molecular Biology Meeting in Madison, Wis., in July. "It seems a good time to get together and learn from the community what they think is most important," Cherry says.

How does nitroglycerin work?

Graphic: Erica P. Johnson
For 130 years, nitroglycerin has been used to relieve angina and mitigate heart failure. What is still not known is how it works, and why it loses efficacy over time. Researchers at Duke University Medical Center, Durham, NC, using a rabbit aorta model, have made strides in deciphering the mysterious molecular mechanisms (Z. Chen, "Identification of the enzymatic mechanism of nitroglycerin bioactivation," Proceedings of the National Academy of Sciences, 99:8306-11, June 11, 2002). Scientists found the enzyme, mitochondrial aldehyde dehydrogenase (mtALDH), which uses a novel reductase action to reduce nitroglycerin to nitrite and 1,2-glyceryl dinitrate; these eventually get converted to nitric oxide (NO), a vasodilator. Using macrophages with properties akin to blood vessels which can be grown in large quantities, the researchers found mtALDH at the center of nitroglycerin's conversion. Jonathan Stamler, Howard Hughes Medical Institute associate investigator and professor of medicine at Duke Medical Center, says that although his team has not worked out every aspect of the pathway, finding the first enzyme required for activation is still a major discovery. "The difficulty will be getting that NO-related molecule out of the mitochondria." Alas, nitroglycerin causes oxidative injury to mitochondria over time, limiting its own biotransformation. Thus, tolerance to the drug builds.

SNPs, aisle three

Image: Erica P. Johnson
UK-based Sciona has been facing difficulties in trying to market a genetic screening service to consumers. You and Your Genes, a service that screens SNPs at nine metabolic pathway genes to create a tailored nutrition and lifestyle recommendation, was pulled from the shelves of The Body Shop retailers in the United Kingdom due to lack of demand, while 13 other retailers refused to stock the product. Biotechnology watchdog, GeneWatch UK, lauds the move, saying the currently unregulated product leads down a slippery slope toward genetic privacy abuses. Manuel Sanchez-Felix, chief technical officer at Sciona, says the company has been proactive in trying to get proper approval, but the Human Genetics Commission's Code of Practice for genetic screening tests was written for testing single-gene disorders. "The regulations need to evolve and change. We're completely in favor of that," Sanchez-Felix says. The commission will recommend that the British Department of Health suspend the current code for retooling. Nevertheless, some scientists question the validity of a product that can offer advice based on a group of genes. Muin Khoury, director, Office of Genomics and Disease Prevention at the Centers for Disease Control and Prevention, Atlanta, calls the marketing of such products rash. "The data are not there, the approach is not there, the protections for people are not there," he says. "Although the concept is okay, the execution at this time for bundling a few genes together to tell people what to do and what to eat is premature." Sanchez-Felix insists that claims about the product are well-supported and points to the company's bibliography (

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