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Archive - Mar 2011

March 14th

Orchid Lures Prey with Scent of Death

Research led by Dr. Timotheüs van der Niet at the University of KwaZulu-Natal in South Africa shows that the South African orchid Satyrium pumilum lures flies into its flowers by mimicking the smell of rotting flesh. A new study comparing the scent of the orchids with that of roadkill was published online on March 13, 2011, in the Annals of Botany. The orchid S. pumilum is found in sandy, moist conditions near small streams across the Cape floral kingdom of South Africa. The flowers are a puzzle. They don't carry any nectar and even if they did, the spurs that would hold it are the wrong shape to feed any visitors. So how do they attract insects to pollinate their flowers? Dr. Van der Niet said: "We know it's common for orchids to deceive insects into pollinating them. We also know that some plant species can mimic carrion to attract flies. What we didn't know was how successful this was. Mimicry is often a very poor way to pollinate a plant. So we set out to observe the plants in the wild and see if we could work out how they were attracting flies." The team staked out a region of farmland with many of the orchids on it. They then went about finding carrion for a comparison. Dr. Van der Niet said: "We didn't kill creatures to entice the flies. Instead we used dassies (rock hyraxes). They're small animals and they look a little like a guinea pig. You can find them almost anywhere in South Africa, and that means you can also find them as roadkill. So we examined the flies visiting the dead dassies, and compared them to the flies visiting the orchids. Because of the high density of orchids we didn't see many flies visiting the flowers, but on the nearby dassie carcass we caught a lot of flies carrying orchid pollen, providing ample 'smoking gun' evidence of how common this interaction was.

Taking Tamoxifen to Prevent Breast Cancer Can Save Lives

Tamoxifen, taken by certain women as a preventive measure against breast cancer, saves lives and reduces medical costs. That is the conclusion of a new study published online on March 14, 2011, in Cancer, a peer-reviewed journal of the American Cancer Society. The study's results suggest that the benefits of tamoxifen to prevent cancer can sufficiently compensate for its side effects in post-menopausal women under age 55 years who have an increased risk of developing breast cancer. Research has shown that tamoxifen can protect against breast cancer for years after treatment ends, but identifying the group of women who can most benefit from the drug as a cancer preventive agent, without experiencing serious side effects, is a challenge. Side effects of the drug can include pulmonary embolism, endometrial cancer, deep vein thrombosis, and cataracts, as well as hot flashes and early menopause. To investigate those women who would benefit the most from taking tamoxifen as a cancer preventive drug, Dr. Peter Alperin, of Archimedes, Inc., in San Francisco, and his colleagues used a mathematical model to simulate a post-menopausal population under age 55 years in a virtual clinical trial comparing tamoxifen treatment with no treatment. The investigators modeled tamoxifen therapy based on an analysis of four randomized, placebo-controlled cancer prevention trials, and they assessed the effects that tamoxifen would have on women's breast cancer risk for 10 years following the end of treatment. Cancer incidences and survival information were taken from the Surveillance Epidemiology and End Results cancer registry, while factors such as non-cancer disease incidences, quality of life, and costs were taken from the medical literature.

March 13th

Single Cell Sequencing Suggests Tumors Evolve in Staccato-Like Bursts

A new method of analyzing cancerous tumors developed by scientists at Cold Spring Harbor Laboratory (CSHL) suggests that tumors may not evolve gradually, but rather in punctuated or staccato-like bursts. It is a finding that has already shed new light on the process of tumor growth and metastasis, and may help in the development of new methods to clinically evaluate tumors. The new analytic method, devised by CSHL Professor Michael Wigler and colleagues, features a process called single cell sequencing (SNS), which enables accurate quantification of genomic copy number within a single cell nucleus. In cancer, portions of the genome are amplified or deleted, giving rise to extra or missing copies of key genes and interfering with mechanisms that normally control cell growth. In a study published online on March 13, 2011, in the journal Nature, "we demonstrated that we can obtain accurate and high-resolution copy number profiles by sequencing a single cell from a cancerous tumor," said Dr. Wigler, "and that by examining multiple cells from the same cancer, we can make inferences about how the cancer evolved and spread." The CSHL team also included Professor W. Richard McCombie, Assistant Professor Alex Krasnitz and Research Professor James Hicks. Nicholas Navin, the paper's first author, was a graduate student while pursuing the research at CSHL and is now Assistant Professor at the MD Anderson Cancer Center in Texas. It has been very difficult for scientists to translate their growing ability to classify tumors at the molecular level into methods and tests that can be used in the clinic to analyze tumors in actual patients.

Major Breakthrough in Materials Design for Hydrogen Storage

Since the 1970s, hydrogen has been touted as a promising alternative to fossil fuels due to its clean combustion —unlike hydrocarbon-based fuels, which spew greenhouse gases and harmful pollutants, hydrogen's only combustion by-product is water. Compared to gasoline, hydrogen is lightweight, can provide a higher energy density, and is readily available. But there's a reason we're not already living in a hydrogen economy: to replace gasoline as a fuel, hydrogen must be safely and densely stored, yet easily accessed. Limited by materials unable to leap these conflicting hurdles, hydrogen storage technology has lagged behind other clean energy candidates. In recent years, researchers have attempted to tackle both issues by locking hydrogen into solids, packing larger quantities into smaller volumes with low reactivity—a necessity in keeping this volatile gas stable. However, most of these solids can only absorb a small amount of hydrogen and require extreme heating or cooling to boost their overall energy efficiency. Now, scientists with the U.S. Department of Energy (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a new composite material for hydrogen storage consisting of nanoparticles of magnesium metal sprinkled through a matrix of polymethyl methacrylate, a polymer related to Plexiglas. This pliable nanocomposite rapidly absorbs and releases hydrogen at modest temperatures without oxidizing the metal after cycling—a major breakthrough in materials design for hydrogen storage, batteries, and fuel cells. "This work showcases our ability to design composite nanoscale materials that overcome fundamental thermodynamic and kinetic barriers to realize a materials combination that has been very elusive historically," said Dr.

Rhodopsin May Also Be Involved in Temperature Sensation

New research from the Mount Sinai School of Medicine has revealed that rhodopsin, a pigment of the retina that is responsible for the first events in the perception of light, may also be involved in temperature sensation. This detection had not been revealed in previous studies. The work emerged from a collaboration between the laboratory of Dr. Andrew Chess, Professor in the Departments of Neuroscience, Developmental and Regenerative Biology and Genetics and Genomic Sciences at Mount Sinai, and the laboratory of Dr. Craig Montell, Professor of Biological Chemistry at Johns Hopkins School of Medicine. Their paper is published in the March 11 issue of Science. The research focused on rhodopsin in Drosophila larvae. The temperature-detection function of rhodopsin allows the Drosophila larvae to move to their preferred temperature of 18 degrees Celsius (64.4 degrees Fahrenheit). This ability depends on a thermosensory signaling pathway that includes a heterotrimeric guanine nucleotide-binding protein, or G-protein. "It is very surprising that rhodopsin has a role in temperature sensation, as it was thought to be completely devoted to its well-known role as a light sensor," said Dr. Chess. "This function of rhodopsin allows temperature discrimination in the comfortable range." This new role for rhodopsin emerged from studies of the process that results in the activation of a temperature-sensor protein known as a TRPA1, which Dr. Montell's group has been studying. The researchers released about 75 larvae onto a plate with two temperature zones. Half of the plate was kept at 18 degrees Celsius and the other half ranged from 14 to 32 degrees Celsius. After ten minutes, the larvae lacking rhodopsin could not discriminate temperatures in comfortable range, just like the larvae lacking TRPA1.

International Project to ID Antibiotics for Tuberculosis

Scientists are collaborating on a new international research project to identify antibiotics that can kill tuberculosis and fight resistant strains. "We want to accelerate the discovery of new compounds that can be turned into effective drugs," said Professor Tony Maxwell from the John Innes Centre, a key player in "More Medicines for Tuberculosis," a new European-centered research project. Two billion people are currently infected with TB and three million die every year. TB causes more deaths than any other infectious disease. Rates are increasing, especially in sub-Saharan Africa, where people with HIV are particularly vulnerable. It is also associated with intravenous drug use and increased rates may be linked to immigration. "The bacterium is difficult to get at," said Professor Maxwell. "It is slow growing, spends a lot of time hidden in cells before it makes itself known, and has very tough cell walls of its own." Treatment is relatively long term, requiring a drug regimen over four to six months. Non-compliance is a problem, exacerbating the challenge caused by resistant strains. "Drug discovery research for tuberculosis is dependent on academic labs and no single lab can do it," said Professor Maxwell. Scientists from 25 labs across Europe will collaborate on the new project as will some groups in the US and India. The John Innes Centre scientists will focus on compounds that target DNA gyrase, a target that they have already established as effective and safe. They will receive compounds from European collaborators including AstraZeneca. They will screen those that knock out DNA gyrase. Their research will continue on those compounds that are effective both against the target (DNA gyrase) and the bacterium.

Leaf Beetle Alters Defense Mechanism for Birch-Feeding Versus Willow-Feeding

Larvae of the leaf beetle Chrysomela lapponica attack two different tree species: willow and birch. To fend off predator attacks, the beetle larvae produce toxic butyric acid esters or salicylaldehyde, whose precursors they ingest with their leafy food. Scientists of the Max Planck Institute for Chemical Ecology in Jena, Germany, and colleagues have now found that a fundamental change in the genome has emerged in beetles that have specialized on birch: The activity of the salicylaldehyde-producing enzyme salicyl alcohol oxidase (SAO) is missing in these populations, whereas it is present in willow feeders. For birch beetles, the loss of this enzyme and thereby the loss of salicylaldehyde is advantagous: the enzyme is not needed anymore because its substrate salicyl alcohol is only present in willow leaves, but not in birch. Birch beetles can therefore save resources instead of producing the enzyme at a cost. First and foremost, however, the loss of salicylaldehyde also means that birch-feeding populations do not betray themselves to their own enemies anymore, that can trace them because of the odorous substance. These new findings were reported online on March 7, 2011, in PNAS. Beetle larvae are part of a food chain. They are attacked by predatory insects and parasites, such as hover flies and bugs, as well as infested by bacteria and fungi. To protect themselves, some leaf beetle larvae have developed interesting defense mechanisms, which function externally and metabolically: In case of danger, they emit substances from their defensive glands in form of vesicles (a short video is available at http://www.ice.mpg.de/ext/735.html). These defensive secretions contain toxins that the larvae sequester from chemical precursors they have ingested with their plant food.

March 12th

Loss of Caspase-2 May Be Protective in Neurodegenerative Disorders

Cell biologists pondering the death of neurons have reported that by eliminating one ingredient from the cellular machinery, they prolonged the life of neurons stressed by a pesticide chemical. The finding identifies a potential therapeutic target to slow changes that lead to neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. The researchers, from The University of Texas Health Science Center San Antonio, found that neurons lacking a substance called caspase-2 were better able to withstand pesticide-induced damage to mitochondria. The research is published in the March 11, 2011 issue of the Journal of Biological Chemistry. Caspase-2 appears to be a master switch that can trigger either cell death or survival depending on the amount of cellular damage, the team found. Neurons that lacked caspase-2 showed an increase in protective activities, including the efficient breakdown of obsolete or used proteins. This process, called autophagy, delays cell death. "This research shows, for the first time, that in the absence of caspase-2, neurons increase autophagy to survive," said study co-author Dr. Marisa Lopez-Cruzan, investigator in the cellular and structural biology department at the Health Science Center. Evidence suggests that mitochondrial dysfunction plays an important role in neuronal death in conditions such as Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), and Huntington's disease. "Identifying initiators in the cell death process is important for determining therapeutic approaches to provide the maximum protection of neurons during neurodegenerative conditions," said senior author Dr. Brian Herman, vice president for research and professor of cellular and structural biology at the Health Science Center. The team studied neurons from young adult mice.

Creativity Appears an Upside to ADHD

A new study in the April 2011 issue of Journal of Personality and Individual Differences found that adults with attention deficit hyperactivity disorder (ADHD) enjoyed more creative achievement than those who didn't have the disorder. "For the same reason that ADHD might create problems, like distraction, it can also allow an openness to new ideas," said Dr. Holly White, assistant professor of cognitive psychology at Eckerd College in St. Petersburg, Florida, and co-author of the paper. "Not being completely focused on a task lets the mind make associations that might not have happened otherwise." Dr. White and Dr. Priti Shah at the University of Michigan gave 60 college students – half of them with ADHD – a series of tests measuring creativity across 10 domains. The ADHD group scored higher across the board. The ADHD group showed more of a preference for brainstorming and generating ideas than the non-ADHD group, which preferred refining and clarifying ideas. The study is a follow-up to one done in 2006, which focused on laboratory measures of creativity and found that ADHD individuals show better performance on tests of creative divergent thinking. "We didn't know if that would translate into real-life achievement," said Dr. Shah. "The current study suggests that it does." [Press release] [Journal of Personality and Individual Differences abstract]

March 11th

Study Shows How Breast Cell Communities Organize into Breast Tissue

A study by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) of the different types of cells that make up the human breast shows that not only do cells possess an innate ability to self-organize into communities, but these communities of different types of cells can also organize themselves with respect to one another to form and maintain healthy tissue. Understanding this ability of different types of cell communities to self-organize into tissue may help explain how the processes of stem cell differentiation and tissue architecture maintenance are coordinated. It might also lead to a better understanding of what goes wrong in cancer. Dr. Mark LaBarge, a cell and molecular biologist in Berkeley Lab’s Life Sciences Division, and Dr. Mina Bissell, a Berkeley Lab Distinguished Scientist also with the Life Sciences Division, carried out a unique study of normal human mammary epithelial cells that had been enriched into pools of the two principal lineages that make up breast tissue – the milk-producing luminals and the myoepithelials that blanket them. In healthy breast tissue, these two lineages organize themselves into an ordered bi-layer. To observe and quantify changes in the distribution of these cell lines with respect to one another over time, Dr. LaBarge, Dr. Bissell and a team of collaborators used a unique “micropatterning” technique, in which the cells were confined to a three-dimensional cylindrical geometry. “We demonstrated that while bi-layered organization in mammary epithelium is driven mainly by the lineage-specific differential expression of the E-cadherin adhesion protein, the expression of the P-cadherin adhesion protein makes additional contributions that are specific to the organization of the myoepithelial layer,” Dr. LaBarge said.