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BioUpdates for February, 2003 by Andrew Tolley Pumping Up the Brain Volume Pumping Up the Brain Volume Exercise is good for you; it keeps you fit and helps your body fend off any number of diseases. Evidence also exists to back up the notion that physical fitness improves cognitive abilities, especially in older adults. Now a new study just published in the Journal of Gerontology by researchers from the University of Illinois at Urbana-Champaign provides the first physical evidence that exercise has an anatomical effect on the brain. Conducting sophisticated MRI scans on a broad group of well-educated seniors with varying degrees of cardiovascular fitness, while allowing for other lifestyle and physical differences, the team detected that the more physically fit individuals retained a higher density of gray and white matter in the frontal, temporal, and parietal cortexes than less fit individuals. The density of gray and white matter does decline with age, but the research clearly indicated the decline to be slower in the more fit individuals. The lead researcher, Arthur L. Kramer of the Beckman Institute for Advanced Science and Technology at Illinois, subsequently conducted a meta-analysis of related research, which led him to conclude that: older adults benefit the most from exercise; a combination of strength and aerobic fitness is more beneficial than one type alone; and, perhaps most significantly, women have more to gain from exercise than men. It would appear a brisk morning walk or jog can help the brain as much as it can the heart and muscles. References: Kramer Arthur F. et al (2003). Aerobic Fitness Reduces Brain Tissue Loss in Aging Humans. Journal of Gerontology A Biol Sci Med Sci 58 (Feb03): M176-M180. Colcombe, Stanley and Kramer, Arthur F. (2003) Fitness Effects on the Cognitive Function of Older Adults: A Meta-Analytic Study Psychological Science. 14 (Mar03). Visit: Journal of Gerontology: Medical Sciences Psychological Science Sperm Like it Hot(ter) In mammals, just how the sperm eventually finds an egg to fertilize has remained something of a mystery. It is not simply a random process where a sperm eventually finds its way through the fallopian tube and stumbles across an egg. Earlier research has shown that a mature egg releases a chemical substance that attracts sperm. However, this process, known as "chemotaxis," is not adequate to answer the question, as the substance works only over relatively short distances. However, Professor Michael Eisenbach of Israel’s prestigious Weizmann Institute now believes he may have discovered the final piece of the puzzle. Basing his thinking on observations showing a temperature differential of 2¾C between the sperm storage site and the site of egg fertilization (the egg site being warmer), he hypothesized that sperm navigated their way to the egg by "thermotaxis." Eisenbach and his team used rabbit sperm in a laboratory simulation to confirm the hypothesis, discovering that a temperature differential of even half a degree was adequate, and that only mature sperm were able to sense the temperature difference. The complete process seems to begin with thermotaxis, which attracts sperm to a point close enough that chemotaxis can guide sperm more precisely to the final destination. This discovery could ultimately be applied to improving the success rate of in vitro fertilization. References: Eisenbach, Michael et al (2003). Thermotaxis of mammalian sperm cells: A potential navigation mechanism in the female genital tract. Nature Medicine 9 (Feb03): 149-150 Visit: Nature Medicine Gene Could Be Knockout Success A recent discovery by researchers from Stanford University Medical Center has the potential to revolutionize the prevention and treatment of heart disease. Investigating the role of the lipase gene family and its proteins in lipid metabolism, the team discovered that the endothelial gene (LIPG) found in blood vessel walls was exerting a strong influence on the regulation of levels of high density lipoproteins (HDL), more commonly known as "good cholesterol." In their work with mice, the teams manipulated the gene and its expression of the protein endothelial lipase to find that there was a striking inverse relationship with levels of HDL. When endothelial expression was increased by insertion of the human LIPG gene, HDL levels fell by 19%. In contrast, when the LIPG gene was knocked out, an increase of 57% in HDL levels was recorded. Based on these results, the team’s leader, Thomas Quertermous, is building a hypothesis that if the gene is knocked out (or at least its effect countered), the probability of the development of heart disease can be significantly decreased, given that HDL has been shown to reduce the risk of disease. He certainly sees this discovery as encouraging research in the development of drugs designed to impact cholesterol levels. References: Quertermous, Thomas et al (2003). Endothelial lipase is a major determinant of HDL level. Journal of Clinical Investigation 111 (Feb03): 347-355. Visit: Journal of Clinical Investigation A Supply to Meet Medical and Ethical Demands The medical promise of pluripotent stem cells continues to inspire researchers to find sources that are free from controversy. Two recently published studies provide evidence that the efforts to find alternative sources continue to bear fruit. At Argonne National Laboratory in Chicago, researchers are very optimistic about the promise their work has for any number of major medical advances. Exposing monocytes (a type of white blood cell) to a growth factor led to them developing into stem cells that the scientists were then able to cultivate into nerve, liver and immune system tissue by using additional growth factors, even after the cells had been stored for some time. The ability to generate stem cells from an individual’s own blood cells, which would theoretically provide an endless supply of genetically matched material, has immense implications. Meanwhile at Kansas State University researchers have been looking to the umbilical cord matrix as a source of stem cells. Known as Wharton’s jelly, the umbilical matrix stem cells of animals and humans have come under scrutiny from the KSU team. The results have been encouraging: stem cells have been propagated, successfully stored for over a year, and engineered to express various proteins, as well as induced to develop into neurons and glia. The team is now working to create cardiac and blood vessel cells. Like the Argonne work, this research could also have significant implications for research and medicine and remove the need for embryonic stem cells. References: Huberman, Eliezer et al (2003). A human peripheral blood monocyte-derived subset acts as pluripotent stem cells. Proceedings of the National Academy of Sciences 100 (Feb03). Mitchell, Kathy E. et al (2003). Matrix Cells from Wharton’s Jelly Form Neurons and Glia. Stem Cells 21 (Jan03): 50-60. Visit: Argonne National Laboratory Press Release Proceedings of the National Academy of Sciences Stem Cells Online Unraveling the Landscape of Proteins The mapping, classification, and cataloguing of information provides the cornerstone of most disciplines. Consequently, the unglamorous work of constructing a three-dimensional global map of the extremely complex world of protein structure will provide a powerful tool for biology and medical researchers, enabling them to accelerate their work and more rapidly interpret their discoveries. Thanks to the efforts of Sung-Hou Kim and colleagues at the Lawrence Berkeley National Laboratory and the University of California at Berkeley, that tool is now in place and promises to be invaluable to researchers all over the world. The work is especially important as the nature of protein folding is as key to protein function as is chemistry. The "map" was constructed using empirical data along with mathematical formulas and its validity is confirmed by how much agreement it shows with the existing system of protein classification, SCOP (Structural Classification of Proteins) which is based on visual observations. Together these two systems also seem to put to rest the debate on how many classes of protein fold structures there really are. Some have argued that there are only three, but the new map mathematically demonstrates that there are actually four, known as alpha helices, beta strands, alpha plus beta, and alpha slash beta. Now, whenever researchers discover a new protein they can turn to the map not only to help them classify it but also to more rapidly understand its likely function, by evaluating it in relation to similar neighboring proteins. Similarly, the map will also assist in the design of safer and more effective drugs. The map is being set up to enable researchers to readily plug new discoveries into what will no doubt be an ever-unfolding database. References: Sung-Hou Kim et al (2003). A global representation of the protein fold space. Proceedings of the National Academy of Sciences 100 (Feb03). Visit: Proceedings of the National Academy of Sciences Structural Classification of Proteins Lawrence Berkeley National Laboratory Press Release University of California at Berkeley Press Release |
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