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Harvard University biologists stumbled upon an unusual trait of at least eleven species of frogs in Africa - they can grow claws. The scientists were intrigued by this finding, not only because it is rare for amphibians to have claws, but also because these are particularly unusual claws. Vertebrate claws typically are covered by a sheath of keratin, or if they are covered by skin, they usually are retractable (like the claws of a cat). In contrast, the claws of the African frogs are small, pointed bones at then ends of the frogs' toes, which are connected to the rest of the toe by a collagen-rich sheath. When threatened, the frogs can then flex a certain foot tendon, and the claw-bone separates from the rest of the toe, and bursts through the skin. The biologists now plan to study how the bone is retracted back into the skin, and how the skin regenerates after the claws have returned to the body.

Primary Source: Blackburn, D. C., et al. (2008). Concealed weapons: erectile claws in African frogs. Biology Letters.

Traditional cancer treatments damage many healthy cells in addition to cancerous cells. To combat this undesirable side effect, researchers at the University of Texas Southwest Medical Center and University of Texas Dallas are experimenting with new methods of treating cancer cells that do not harm healthy cells. In order to target cancer cells, the researchers are working with immune system proteins called monoclonal antibodies that bind to specific sites on cancer cells. They attached the antibodies to carbon nanotubes (tiny cylinders of carbon atoms), thus creating nanotubes that bind to the surface of cancerous cells, but not healthy cells. When exposed to near-infrared light (a wavelength of light that is invisible to the human eye and can penetrate human tissue up to 1.5 inches), the carbon nanotubes heat up and "cook" the cancer cells, effectively and selectively killing them. Although this technique has not yet been tested in humans, researchers are hopeful that it may greatly improve cancer treatments in the future.

Primary Source: Chakravarty, S. et al. (2008). Thermal ablation of tumor cells with antibody-functionalized single-walled carbon nanotubes. Proceedings of the National Academy of Sciences, 105: 8697-8702.

In 1963, several seeds were discovered at the site of an ancient fortress in present-day Israel. Researchers believe that the seeds came from the Judean date palm, a species which had been extinct for centuries. One of the seeds was germinated in 2005, giving rise to a plant that researchers named Methuselah, after the oldest person mentioned in the Bible. Scientists recently reported that carbon dating of seed fragments from Methuselah confirm that the seed is 2,000 years old, making it the oldest sprouted seed in history. Preliminary genetic studies suggest that Methuselah shares about half of its genetic code with modern date plants. Now, scientists are waiting to see if Methuselah is female to determine if it might be used to resurrect the long-extinct species.

Primary Source: Sallon, S. et al. (2008). Germination, genetics, and growth of an ancient date seed. Science, 320: 1464.

One of the most fundamental concepts in biology is the cell theory, which holds that cells are the basic components of living organisms. No one knows, however, how the first cell-like structures arose (approximately 3 to 4 million years ago), what they looked like, or how they continued to grow and divide. Recently, scientists at Harvard University reported the creation of model "protocells" that contain genetic material surrounded by a fatty acid membrane. The membrane allows essential nutrients, including the chemicals the protocells need to build and copy their genetic material, to enter the structure, without the need for protein pumps or channels. Jack Szostak, lead researcher on the project, commented that "we have come a little closer to our goal of making a functional protocell that, in the right environment, is able to grow and divide on its own." This work provides insight into the features of the primitive cells that gave rise to Earth's early life forms.

Primary Source: Mansy, S.S., et al. (2008). Template-directed synthesis of a genetic polymer in a model protocell. Nature.

Related Resources on BioEd Online:
Downloadable slide: What is a Cell?

Our bodies contain biological "clocks" that regulate our normal patterns of activity, including our sleep-wake cycle and metabolism. Disruption of the body's internal rhythms, known as circadian rhythms, is linked to a number of problems including insomnia, depression and cancer. Circadian rhythms, which normally follow a cycle of about 24 hours, are sensitive to, and adjusted by changes in the light-dark cycle. The "master clock" that monitors these changes is found in an area of the brain known as the superchiasmatic nucleus of the hypothalamus. This group of cells receives signals from the eyes, processes changes in the daily cycle of light and dark, and serves as the body's primary timekeeper. Previously, researchers had discovered a second internal clock that monitors meal-times rather than exposure to daylight. Now, researchers have discovered that this food-based clock also is located in the hypothalamus, specifically, in the dorsomedial hypothalamic nucleus. Evidence suggests that when food is scarce, the "food clock" can override the "light clock" and change an animal's sleeping patterns so that opportunities to eat are not missed. These results provide greater understanding of how different areas of the brain are involved in setting the body's circadian rhythms. Although further work is necessary, this new knowledge ultimately may be useful in addressing human problems such as jet lag and difficulties adjusting to a shift work schedule.

Primary Source: Fuller, P.M., Lu, J., & Saper, C.B. (2008). Differential rescue of light- and food-entrainable circadian rhythms. Science, 320:1074-1077.

Related Resources on BioEd Online:
Teacher's Activity Guide: Sleep and Daily Rhythms
Downloadable slide set: Sleep and Human Performance (NSBRI)

Researchers long have attempted to build the ultimate photonic crystal, and have met with little success. The ideal or "champion" photonic crystal would have the same structure as diamonds. This structure would allow the crystal to manipulate visible light efficiently, a necessary function for future, ultra-fast optical computers that will run on light rather than electricity. Recently, scientists discovered that the scales of a Brazilian beetle (Lamprocyphus augustus) have a "champion" or diamond-like architecture - the exact crystal structure that scientists have been trying to create. These scales form the beetle's exoskeleton and produce its iridescent appearance. According to Michael Bartl, leader of the team that performed this work, "Nature has simple ways of making structures and materials that are still unobtainable with our million-dollar instruments and engineering strategies." Unfortunately, the scales themselves cannot be used in technological devices but scientists now are working to develop a synthetic version of the beetle's "champion crystals."

Alzheimer's disease (AD) is a progressive degenerative brain disorder characterized by memory impairment and disturbances in the ability to reason and plan. It is estimated that more than 20 million people worldwide have the disease, for which there currently is no cure. One of the hallmark features of AD, and other neurodegenerative disorders, is the existence of amyloid fibrils - tentacle-like structures composed of misfolded, insoluble aggregates of protein. In AD, these amyloid fibrils are built from a peptide known as amyloid-beta (A-beta) and are associated with neurodegeneration. Despite their prevalence in a number of degenerative diseases, many important details of the structure of these amyloid fibrils have remained unknown. Recently, scientists from Brandeis University in Waltham, Massachusetts and the Leibniz Institut in Jena, Germany created a high resolution, three-dimensional image of an A-beta amyloid fibril. According to Nikolaus Grigorieff, senior author of the study, "People have been guessing for decades what these fibrils look like, but now we have an actual 3D image." Researchers hope that this new structural information will help uncover the role these fibrils play in AD, and other neurodegenerative disorders, and ultimately aid in the development of drugs that treat and prevent these diseases.

Primary Source: Sachse, C., Fandrich, M., & Grigorieff, N. (2008). Paired beta-sheet structure of an A-beta (1-40) amyloid fibril revealed by electron microscopy. Proceedings of the National Academy of Sciences, 105:7462-7466.

Myosin 2 is a motor protein found in muscle cells, where it plays an important role in muscle contraction. Recently, scientists from the University of Leeds reported a surprising discovery: myosin 2 protein found in scallops is structurally identical to myosin 2 protein found in turkeys, despite the fact that these two creatures are separated by more than 600 million years of independent evolution. This finding suggests that the structure of this motor protein could be more important than many previously appreciated. According to Peter Knight, senior author of the study, "In evolution, if something is not essential to the survival of an organism, it is not conserved." This finding likely will lead to more detailed investigations of the role of myosin 2 in humans, particularly as it relates to human health. Already, it is known that changes in the composition of myosin in human muscle tissue can lead to fatal problems such as brain aneurisms and cardiac arrest. In order to tackle these and other problems related to myosin 2, scientists hope to learn more about the structure and function of the protein.

Primary Source: Jung, H.S. et al. (2008). Conservation of the regulated structure of folded myosin 2 in species separated by at least 600 million years of independent evolution. PNAS, 105: 6022-6026.

Related Resources on BioEd Online:
Downloadable slide set: Maintaining Muscle Mass in Space
Teacher Activity Guide: The Science of Muscles and Bones

Livestock are recognized as a significant source of the world's greenhouse gas emissions. To address this issue, scientists in Australia and New Zealand are working to develop a new type of grass designed to reduce the amount of methane produced by cows. When cellulose, the structural component of the primary cell wall of green plants, is digested in the cow gut, methane gas is created as a by-product. It is estimated that one dairy cow can produce between 550-700 liters of methane in a single day. To reduce these emissions, scientists are trying to create more easily digestible grass by suppressing the expression of a specific grass enzyme (O-methyl transferase). The modification should not compromise the structural properties of the grass and may allow it to grow in hotter climates. While some researchers believe that this strategy could lead to reduced methane production in cows, others are skeptical, and some even have suggested that this approach will lead to an increase in the absolute levels of methane released by cows. Field tests are being planned to investigate whether or not this will be an effective approach to combat greenhouse gas emissions of the agricultural industry.

Related Resources on BioEd Online:
Teacher's Activity Guide: Global Resources