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Archive - 2009

October 5th

Small Body Size, High Mortality Rate, and Early Sexual Maturity in Pygmies

A new study suggests that high mortality rates in small-bodied people, commonly known as pygmies, may be part of the reason for their small stature. The study, by Dr. Jay Stock and Dr. Andrea Migliano, both of the University of Cambridge, may help unravel the mystery of how small-bodied people got that way. Adult males in small-bodied populations found in Africa, Asia, and Australia are less than four feet, 11 inches tall, which is about one foot shorter than the average adult male in the U.S. Why people in these populations are so small remains a mystery, but several hypotheses have been proposed. Some scientists think that small bodies provide an evolutionary advantage under certain circumstances. For example, a smaller body needs less food—a good thing in places where food supplies are inconsistent. Small bodies also may provide an advantage in getting around in thickly forested environments. Recently, however, a new hypothesis has come to the fore suggesting that reproductive consequences of high mortality rates may explain small body size. If death comes at an early age, then natural selection would favor those who are able to reproduce at an early age. But early sexual maturity comes with a cost. When the body matures early, it diverts resources to reproduction that otherwise would have gone to growth. So small body size could be essentially a side effect of early sexual maturity. Stock's and Migliano's study provides the first long-term evidence for the mortality hypothesis. The article appears in the October issue of Current Anthropology. [Press release] [Current Anthropology abstract]

October 1st

New Clue to Tuberculosis

Scientists have discovered a potential chink in the armor of the organism that causes tuberculosis in humans. They have shown that the organism (Mycobacterium tuberculosis) produces a compound (edaxadiene) that provides a defense mechanism against the killing power of macrophages that normally engulf and destroy harmful bacteria. The scientists have, in addition, identified molecules that inhibit the edaxadiene-producing enzyme and therefore have the potential to reduce the tuberculosis organism’s resistance to macrophage attack. The researchers cautioned, however, that finding an inhibitor that works outside of the test tube, and in humans, and is stable, and can be ingested safely by humans, and can help kill tuberculosis is a process that may take a decade. Nevertheless, Dr. Reuben Peters, senior author of the study, said, "This is the project where I tell my students, 'If we can make even just a 1 percent impact, we can save 15,000 - 20,000 lives a year.' That is really a significant contribution towards alleviating human suffering.” Tuberculosis is a contagious disease that is on the rise, killing 1.5 to 2 million people worldwide annually. Portions of this new work are reported in the August 28 issue of the Journal of Biological Chemistry and are slated to be the cover subject of an upcoming issue of the Journal of the American Chemical Society. [Press release] [JBC abstract]

September 30th

Hormone May Help Plants Rid Themselves of Pesticides

Scientists in China have discovered that a natural plant hormone, applied to crops, can help plants eliminate residues of certain pesticides. The researchers noted that pesticides are essential for sustaining food production for the world's growing population. Farmers worldwide use about 2.5 million tons of pesticides each year. Scientists have been seeking new ways of minimizing pesticide residues that remain in food crops after harvest — with little success. Previous research suggested that plant hormones called brassinosteroids (BRs) might be an answer to the problem. In the current work, the researchers treated cucumber plants with one type of BR, and then treated the plants with various pesticides, including chloropyrifos (CPF), a broad-spectrum commercial insecticide. The BR significantly reduced the pesticides’ toxicity and residues in the plants, the scientists said. BRs may be "promising, environmentally friendly, natural substances suitable for wide application to reduce the risks of human and environmental exposure to pesticides," the scientists noted. The substances do not appear to be harmful to people or other animals, they added. This work was reported in the September 23 issue of the Journal of Agricultural and Food Chemistry published by the American Chemical Society. [Press release] [JAFC abstract]

September 29th

Olive Oil Compound May Aid Treatment/Prevention of Alzheimer’s

Scientists have discovered that a naturally-occurring compound (oleocanthal) found in extra-virgin olive oil alters the structure of neurotoxic proteins (ADDLs or beta-amyloid oligomers) believed to contribute to the debilitating effects of Alzheimer's disease. The structural change impedes the proteins' ability to damage brain nerve cells. "Binding of ADDLs to nerve cell synapses is thought to be a crucial first step in the initiation of Alzheimer's disease. Oleocanthal alters ADDL structure in a way that deters their binding to synapses," said Dr. William L. Klein, a co-leader of the research team. "Translational studies are needed to link these laboratory findings to clinical interventions." An unexpected finding was that oleocanthal makes ADDLs into stronger targets for antibodies. This action establishes an opportunity for creating more effective immunotherapy treatments, which use antibodies to bind to and attack ADDLs. Future studies to identify more precisely how oleocanthal changes ADDL structure may increase understanding of the pharmacological actions of oleocanthal and such pharmacological insights could provide discovery pathways related to disease prevention and treatment. This work was reported in the October 15 issue of Toxicology and Applied Pharmacology. [Press release] [TAP abstract]

September 28th

Prion Proteins Appear to Share Evolutionary Origin with ZIP Proteins

Suggestive evidence as to the evolutionary ancestry of prion proteins has been obtained by researchers at the University of Toronto and collaborating institutions. Prions are responsible for such devastating diseases as “mad cow disease” (bovine spongiform encephalopathy) and Creutzfeldt-Jakob disease. The researchers’ analysis suggests that the prion gene is descended from the more ancient ZIP family of metal ion transporters. Members of the ZIP protein family are well known for their ability to transport zinc and other metals across cell membranes. The researchers initially demonstrated the physical proximity of two metal ion transporters, ZIP6 and ZIP10, to mammalian prion proteins in living cells. As with the normal cellular prion protein, ZIP6 and ZIP10 exhibit widespread expression in biological tissues with high transcript levels in the brain. The scientists then made the startling discovery that prion and ZIP proteins contain extensive stretches of similar amino acid sequence. The researchers next documented that the respective segments within ZIP and prion proteins are computationally predicted to acquire a highly similar three-dimensional structure. Finally, the team uncovered multiple additional commonalities between ZIP and prion proteins, which led them to conclude that these molecules are evolutionarily related. Overall, this work holds promise for efforts to reveal the physiological function of members of the prion protein family and may provide insights into the origins and underlying constraints of the conformational changes associated with prion diseases. This work was published on September 28 in PLoS ONE. [Press release] [PLoS ONE article]

Chemicals Prevent Premature Termination of Protein Synthesis in Genetic Disease

Using high-throughput screening of 35,000 compounds, scientists at UCLA have identified two compounds (nonaminoglycosides) that may have the potential to correct certain genetic diseases that are caused by the premature termination of protein synthesis due to nonsense mutations in the coding DNA. "When DNA changes, such as nonsense mutations, occur in the middle rather than the end of a protein-producing signal, they act like a stop sign that tells the cell to prematurely interrupt protein synthesis," explained Dr. Richard Gatti, senior author of the study. "These nonsense mutations cause the loss of vital proteins that can lead to deadly genetic disorders." Dr. Gatti's lab specializes in studying ataxia-telangiectasia (A-T), a progressive neurological disease that strikes young children, often killing them by their late teens or early 20s. "Of the dozens of active chemicals we discovered, only two were linked to the appearance and function of ATM, the protein missing from the cells of children with A-T," said Dr. Liutao Du, the first author of the study, in speaking about cellular studies that were conducted. "These two chemicals also induced the production of dystrophin, a protein that is missing in the cells of mice with a nonsense mutation in the muscular dystrophy gene." The UCLA team is optimistic that its discovery will aid pharmaceutical companies in creating drugs that correct genetic disorders caused by nonsense mutations. This could potentially affect one in five patients with most genetic diseases, including hundreds of thousands of people suffering from incurable diseases. Because nonsense mutations can lead to cancer, such drugs may also find uses in cancer treatment. This study was published in the September 28 issue of the Journal of Experimental Medicine.

September 24th

Potato Genome First-Draft Sequence Released

An international consortium has released the first draft of the potato genome sequence. "The potato is the most important vegetable worldwide," said Dr. Robin Buell, a member of the consortium. "This first draft that is being released will help breeders improve yield, quality, disease resistance, and nutritional value." The Potato Genome Sequencing Consortium, an international team of 39 scientists from 14 countries, began work on the potato genome project in 2006. The complete sequence is estimated to be 840 million base pairs, about one-quarter the size of the human genome. The draft sequence, which covers 95 percent of potato genes, is available at http://www.potatogenome.net and will be updated over the next six months. [Press release]

September 23rd

Retinal Implant May Restore Some Vision

Researchers at MIT, together with collaborators, have developed a prototype retinal implant for people who have lost their vision from retinitis pigmentosa or age-related macular degeneration, two of the leading causes of blindness. The implant would help restore some vision by electrically stimulating the nerve cells that normally carry visual input from the retina to the brain. Patients who receive the implant would wear a pair of glasses with a camera that sends images to a microchip attached to the eyeball. The glasses also contain a coil that wirelessly transmits power to receiving coils surrounding the eyeball. When the microchip receives visual information, it activates electrodes that stimulate nerve cells in the areas of the retina corresponding to the features of the visual scene. The electrodes directly activate optical nerves that carry signals to the brain, bypassing the damaged layers of retina. The chip would not restore normal vision, but could help blind people more easily navigate a room or walk down a sidewalk. "Anything that could help them see a little better and let them identify objects and move around a room would be an enormous help," said Dr. Shawn Kelly, a member of the research team. The researchers hope to start testing the prototype in blind patients within the next three years, after some safety refinements are made. The work was published in the October issue of the IEEE Transactions on Biomedical Engineering. [Press release]

Whale Skeletons Home to Nine New Species

A recent Ph.D. thesis from the University of Gothenburg in Sweden, reports the identification of nine new species of bristleworm, a type of worm typically found on whale skeletons. Some previously identified species of bristleworm are so specialized in eating dead whales that they would have problems surviving elsewhere. One species uses its root system to penetrate the whale bones when searching for food. Other species specialize in eating the thick layers of bacteria that quickly form around the bones. When a whale dies, it sinks to the seafloor and becomes food for an entire ecosystem. Dead whales constitute an unpredictable food source; it is impossible to know when and where a whale is going to die, and when it does, the food source does not last forever. Nevertheless, some marine species have specialized in feeding on whale cadavers. A dead whale is an enormous source of nutrients. In fact, one cadaver offers the same amount of nutrients that normally sinks from the surface to the seafloor in 2,000 years, and this is of great benefit to innumerable species: First, the meat is eaten by, for example, sharks and hagfish, then tremendous numbers of various organisms come to feast on the skeleton. Four of the new bristleworm species were found on whale cadavers placed at a depth of 125 meters in the new national park Kosterhavet off the coast of Strömstad, Sweden. The other five species feed on whale bones in the deep waters off the coast of California. The family tree of bristleworms was explored using molecular data. The DNA analyses showed that there are several so-called “cryptic” bristleworm species, meaning species that, despite appearing identical, differ very much genetically.

September 19th

New Rabies Vaccine May Require Only One Shot

Scientists have developed a rabies vaccine that may require only one shot to prevent the fatal disease. The new vaccine is made from live virus from which a key viral gene [the matrix (M) gene] has been removed so that the virus is inhibited from reproducing in the body. This vaccine appeared safe and effective in tests in mice and non-human primates. The immune response induced with this vaccine is so substantial that only one inoculation may be sufficient, according to Dr. James McGettigan, senior author of the study. The current standard rabies vaccine is made from inactivated virus and the normal post-exposure regimen is five shots of vaccine and one of rabies immunoglobulin over a period of 28 days. Worldwide, the annual number of rabies-related deaths is estimated to be 40,000 to 70,000. The disease is endemic in developing areas, where the six-shot post-exposure regimen is not feasible for many people due to cost and availability. According to the World Health Organization, approximately 10 million people worldwide receive the post-exposure regimen, which presents a financial burden to both industrialized and developing countries. "Developing countries do not have the resources to vaccinate people six times after exposure, so many of these 10 million do not receive the full regimen," said Dr. McGettigan. "Therefore, simpler and less expensive vaccine regimens are needed. The alternative may also be to treat people pre-exposure, as they are with many of the current vaccines used. Although our vaccine was tested primarily to be a post-exposure vaccine, the data we collected show it would be effective as a pre-exposure vaccine as well." This research was published online on September 18 in the Journal of Infectious Diseases.