October 23, 2007, 9:10 PM CT

Adult stem cells lack key regulator

The protein Oct4 plays a major role in embryonic stem cells, acting as a master regulator of the genes that keep the cells in an undifferentiated state. Unsurprisingly, scientists studying adult stem cells have long suspected that Oct4 also is critical in allowing these cells to remain undifferentiated. Indeed, more than 50 studies have reported finding Oct4 activity in adult stem cells.

But those findings are misleading, as per research in the lab of Whitehead member and MIT biology professor Rudolf Jaenisch.

In a paper published online in Cell Stem Cells on Oct. 10, postdoctoral fellow Christopher Lengner has shown that Oct4 is not mandatory to maintain mouse adult stem cells in their undifferentiated state, and that adult tissues function normally in the absence of Oct4. Furthermore, using three independent detection methods in several tissue types in which Oct4-positive adult stem cells had been reported, Lengner found either no trace of Oct4, or so little Oct4 as to be indistinguishable from background readings.

This means that pluripotency, the ability of stem cells to change into any kind of cell, is regulated differently in adult and embryonic stem cells.

"This is the definitive survey of Oct4," said Jaenisch. "It puts all those claims of pluripotent adult stem cells into perspective"......... Posted by: Sean      Read more         Source

October 23, 2007, 8:46 PM CT

The Sensitive Side of Carbon Nanotubes

Blocks of carbon nanotubes can be used to create effective and powerful pressure sensors, as per a new study by scientists at Rensselaer Polytechnic Institute.

Taking advantage of the material's unique electrical and mechanical properties, scientists repeatedly squeezed a 3-millimeter nanotube block and discovered it was highly suitable for potential applications as a pressure sensor. No matter how a number of times or how hard they squeezed the block, it exhibited a constant, linear relationship between how much force was applied and electrical resistance.

"Because of the linear relationship between load and stress, it can be a very good pressure sensor," said Subbalakshmi Sreekala, a postdoctoral researcher at Rensselaer and author of the study.

A sensor incorporating the carbon nanotube block would be able to detect very slight weight changes and would be beneficial in any number of practical and industrial applications, Sreekala said. Two potential applications are a pressure gauge to check the air pressure of automobile tires, and a microelectromechanical pressure sensor that could be used in semiconductor manufacturing equipment.

Despite extensive research over the past decade into the mechanical properties of carbon nanotube structures, this study is the first to explore and document the material's strain-resistance relationship. The paper, titled "Effects of compressive strains on electrical conductivities of a macroscale carbon nanotube block," was published in a recent issue of Applied Physics Letters......... Posted by: Kevin      Read more         Source

October 22, 2007, 8:47 PM CT

Quantum cascade laser nanoantenna

Cambridge, Mass. October 22, 2007 In a major feat of nanotechnology engineering scientists from Harvard University have demonstrated a laser with a wide-range of potential applications in chemistry, biology and medicine. Called a quantum cascade (QC) laser nanoantenna, the device is capable of resolving the chemical composition of samples, such as the interior of a cell, with unprecedented detail.

Spearheaded by graduate students Nanfang Yu, Ertugrul Cubukcu, and Federico Capasso, Robert L. Wallace Professor of Applied Physics, all of Harvards School of Engineering and Applied Sciences, the findings will be published as a cover feature of the October 22 issue of Applied Physics Letters. The scientists have also filed for U.S. patents covering this new class of photonic devices.

The lasers design consists of two gold rods separated by a nanometer gap (a device known as an optical antenna) built on the facet of a quantum cascade laser, which emits invisible light in the region of the spectrum where most molecules have their tell tale absorption fingerprints. The nanoantenna creates a light spot of nanometric size about fifty to hundred times smaller than the laser wavelength; the spot can be scanned across a specimen to provide chemical images of the surface with superior spatial resolution......... Posted by: Kevin      Read more         Source

October 22, 2007, 8:43 PM CT

Rise in atmospheric CO2 accelerates as economy grows

Human activities are releasing carbon dioxide faster than ever, while the natural processes that normally slow its build up in the atmosphere appear to be weakening. These conclusions are drawn in a new study in the early online edition of the Proceedings of the National Academy of Sciences,* October 22-26. The report states that together, these effects characterize a carbon cycle that is generating stronger-than-expected climate forcing sooner than expected.

Between 2000 to 2006, human activities such as burning fossil fuels, manufacturing cement, and tropical deforestation contributed an average of 4.1 billion metric tons of carbon to the atmosphere each year, yielding an annual growth rate for atmospheric carbon dioxide of 1.93 parts per million (ppm). This is the highest since the beginning of continuous monitoring in 1959, states the report. The growth rate of atmospheric carbon dioxide is significantly larger than those for the 1980s and 1990s, which were 1.58 and 1.49 ppm per year, respectively. The present atmospheric concentration of carbon dioxide is 381 ppm, the largest concentration in the last 650,000 years, and probably in the last 20 million years.

While the worldwide acceleration in carbon dioxide emissions had been previously noted, the current analysis provides insights into its causes. The new twist here is the demonstration that weakening land and ocean sinks are contributing to the accelerating growth of atmospheric CO₂, says co-author Chris Field, director of the Carnegie Institutions Department of Global Ecology......... Posted by: Jaison      Read more         Source

October 21, 2007, 10:11 PM CT

Earth from Space: Birth of an iceberg

This animation, comprised of images acquired by Envisat's Advanced Synthetic Aperture Radar (ASAR) instrument, shows the breaking away of a giant iceberg from the Pine Island Glacier in West Antarctica. Spanning 34 km in length by 20 km in width, the new iceberg covers an area nearly half the size of Greater London.

The animation highlights the movement in the area between September 2006 and October 2007. The Pine Island Glacier is visible stretching from the right of the image to the centre. The tongue of Pine Island is shown moving inland between September 2006 and March 2007. Between April and May 2007, the detached iceberg in front of Pine Island moves significantly. Also in May 2007, a crack in Pine Island becomes visible. By October, the new iceberg has completely broken away.

Several different processes can cause an iceberg to form, or 'calve', such as action from winds and waves, the ice shelf grows too large to support part of itself or a collision with an older iceberg. Since Pine Island Glacier was already floating before it calved, it will not cause any rise in the world sea level.

Iceberg calving like this occurs in Antarctica each year and is part of the natural lifecycle of the ice sheet. A 34-year long study of the glacier has shown that a large iceberg breaks off roughly every 5-10 years. The last event was in 2001......... Posted by: Tyler      Read more         Source

October 21, 2007, 10:09 PM CT

The solution to a 7-decade mystery

A Florida State University researcher has helped solve a scientific mystery that stumped chemists for nearly seven decades. In so doing, his teams findings may lead to the development of more-powerful computer memories and lasers.

Naresh S. Dalal, the Dirac Professor of Chemistry and Biochemistry at FSU, recently collaborated with three colleagues, Jorge Lasave, Sergio Koval and Ricardo Migoni, all of the Universidad Nacional de Rosario in Argentina, to determine why a certain type of crystal known as ammonium dihydrogen phosphate, or ADP, behaves the way it does.

ADP was discovered in 1938, Dalal said. It was observed to have some unusual electrical properties that werent fully understood -- and for nearly 70 years, researchers have been perplexed by these properties. Using the supercomputer at SCRI (FSUs Supercomputer Computations Research Institute), we were able to perform in-depth computational analyses that explained for the very first time what causes ADP to have these unusual properties.

ADP, like a number of crystals, exhibits an electrical phenomenon known as ferroelectricity. Ferroelectric materials are analogous to magnets in that they maintain a positively charged and a negatively charged pole below a certain temperature that is characteristic for each compound......... Posted by: Sarah      Read more         Source

Fri, 19 Oct 2007 02:26:07 GMT

Laetiporus gilbertsonii

A thanks to Mike Bush (former director of Lotusland) for sending along today's photograph in an email with the subject line “30mph stopper!”. Mike now has a weblog, BushBlog where he has written about this Fungus Amongus in Santa Barbara and then provides an update on its fate (hint: a dinner plate).

The eastern North American species of chicken-of-the-woods has previously been featured on BPotD, Laetiporus sulphureus. Prior to the start of this decade, conventional thought was that all Laetiporus in North America were one species, L. sulphureus. However, a closer look revealed that there were multiple species, and so Laetiporus sulphureus has been split up. In the case of today's fungus, Laetiporus gilbertsonii is to-the-eye indistinct from L. sulphureus. Grown in culture, however, it will not reproduce with the eastern North American L. sulphureus, making it biologically distinct. By some definitions, that is enough to classify it as a separate species.

In his weblog entry, Mike mentioned that this fungus was growing on a Eucalyptus. Knowing the substrate a fungus is growing on is often useful in identifying it, and that's the case here, as it helped eliminate the conifer-loving Laetiporus conifericola. For more on Laetiporus, visit Michael Kuo's page on Laetiporus sulphureus and relatives. The Fungi of California site provides additional information and more photographs: Laetiporus gilbertsonii.

Photography resource link: The Garden at Night: A Photographic Journey by photographer Linda Rutenberg. Linda visited 19 botanical gardens in the US and Canada and photographed them at night (and yes, UBC Botanical Garden is one of them!). I've found two newspaper articles about her project and book, if you'd like to read more: Moonlight transforms the ordinary into things of beauty via the Montreal Gazette and 'Lady of the Night' Rutenberg vividly captures world of darkness from the Montreal Chronicle. (PS: I've added the book to UBC BG's Amazon store (USA and elsewhere | Canada | UK) if you are interested in purchasing it. I'll be buying a copy.)

For those readers in California, I note that Linda is giving a night photography workshop in San Francisco and lectures at Descanso and Huntington gardens. Posted by: Daniel Mosquin      Read more     Source

October 17, 2007, 8:27 PM CT

Pine bark extract boosts nitric oxide production

A study would be reported in the October edition of High blood pressure Research reveals Pycnogenol, (pic-noj-en-all), an antioxidant plant extract from the bark of the French maritime pine tree, helps individuals by enhancing healthy nitric oxide (NO) production which leads to an increase in blood flow and oxygen supply to muscles.

Nitric oxide, a key cardiovascular chemical produced by the body, increases blood flow that serves to deliver more nutrients and oxygen to the muscles, helping muscles to cope with increased physical activity and build when subjected to regular elevated labor.

This study suggests that when taking Pycnogenol, more NO is provided in response to neurotransmitters allowing for better expansion of arteries to carry more blood. This process serves to meet the enhanced oxygen demand of the performing muscle and avoid anaerobic metabolism, said Dr. Yukihito Higashi, lead researcher of the study. These results also lead me to determine that Pycnogenol will be a useful natural alternative treatment in various diseases in which oxidative stress is involved in the pathogenesis.

The double-blind, randomized, placebo study was held at the Hiroshima University Graduate School of Biomedical Sciences in Japan. Every day for two weeks young healthy men either took 180 mg Pycnogenol or a placebo. To identify Pycnogenols effect on the release of NO, an inhibitor of the amino acid L-arginine was infused in patients, which restricts the expansion of arteries in response to the neurotransmitter acytelcholine......... Posted by: Sarah      Read more         Source

October 17, 2007, 8:20 PM CT

Fossilized cashew nuts reveal Europe was important route

Cashew nut fossils have been identified in 47-million year old lake sediment in Gera number of, revealing that the cashew genus Anacardium was once distributed in Europe, remote from its modern native distribution in Central and South America. It was previously proposed that Anacardium and its African sister genus, Fegimanra, diverged from their common ancestor when the landmasses of Africa and South America separated. However, groundbreaking new data in the recent issue of the International Journal of Plant Sciences indicate that Europe may be an important biogeographic link between Africa and the New World.

The occurrence of cashews in both Europe and tropical America suggests that they were distributed in both North America and Europe during the Tertiary and spread across the North Atlantic landbridge that linked North America and Europe by way of Greenland before the rifting and divergence of these landmasses, explain Steven R. Manchester (University of Florida), Volker Wilde (Forschungsinstitut Senckenberg, Sektion Palaeobotanik, Frankfurt am Main, Gera number of), and Margaret E. Collinson (Royal Holloway University of London, UK). They apparently became extinct in northern latitudes with climatic cooling near the end of the Tertiary and Quaternary but were able to survive at more southerly latitudes......... Posted by: William      Read more         Source

October 17, 2007, 8:13 PM CT

World's potential to produce biodiesel

What do the countries of Thailand, Uruguay and Ghana have in common" They all could become leading producers of the emerging renewable fuel known as biodiesel, says a study from the University of Wisconsin-Madison Nelson Institute for Environmental Studies.

The ease of manufacturing biodiesel from vegetable oils and animal fats has made it one of the most promising, near-term alternatives to fossil fuels. Seeking to understand which nations are best positioned today to enter the burgeoning biodiesel market, scientists Matt Johnston and Tracey Holloway of the Nelson Institute's Center for Sustainability and the Global Environment (SAGE) ranked 226 countries as per their potential to make large volumes of biodiesel at low cost.

Reported online today (Oct. 17) in Environmental Science and Technology, the analysis uncovered a number of of the usual suspects, including the United States, a top soybean grower; and Brazil, already a major biodiesel producer. The Netherlands, Gera number of, Belgium and Spain also cracked the top ten in overall volume potential.

But the scientists say the study's true motivation was to identify developing countries that already export significant amounts of vegetable oil for profit, but may not have considered refining it into biodiesel. By exporting biodiesel - a higher value commodity - these countries could improve their trade balances, says Johnston, or use the fuel to offset their own energy needs......... Posted by: Kevin      Read more         Source