Science Roundup August 2002
Welcome to the latest issue of Science Roundup!
August 30, 2002
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Contents of this issue:

The Challenge of Sustainable Development
How a Fungus Sees the Light
Genes, Abuse, and Violence
Genomics Reveals Evolutionary Clues
Toward Nerve Regeneration
Tool-Making Crows
Cat and Bird Mating Tales
A Snake and Newt Arms Race
Progress in Green Chemistry
Steering Electrons with Light
Vibrationally Excited Water
The Soft Side of Materials Science
Earth Shifts Its Weight
A Warm Polar Outlook


The Challenge of Sustainable Development
http://www.sciencemag.org/feature/data/sust/index.shtml

In anticipation of the World Summit on Sustainable Development, which began in late August, the 9 Aug 2002 Science featured a collection of articles that examined how science can assist in constructing a sustainable world. In an opening Editorial, A. Leshner, the chief executive of AAAS, commented on the necessity of bringing science and technology to developing countries if we hope to ever achieve sustainability. That sentiment was echoed in the 2002 AAAS Presidential Address by P. H. Raven, titled "Science, Sustainability, and the Human Prospect." News Focus articles discussed sustainable agriculture in Amazonian rainforests and the difficulty of gleaning the complete information needed to forecast future water scarcity. A report by Achard et al. (accompanied by a news story by J. Kaiser) analyzed satellite data to determine deforestation rates of the world's tropical forests. And Balmford et al., reviewing more than 300 case studies, determined that the economic benefits of effective global conservation programs outweigh the costs by at least 100 to 1.


How a Fungus Sees the Light

Light keeps biological clocks ticking, in humans, animals -- even fungi. The fungus Neurospora crassa, for example, not only requires blue light to entrain its circadian clock, but also depends on light for physiological processes such as growth, spore formation, and making pigments. Until now, scientists have understood little about how the fungus actually perceives light. Two reports in the 2 Aug 2002 Science provided convincing evidence that the answer lies in White Collar-1 (WC-1), a protein with a fascinating dual function: it acts as a photoreceptor and absorbs light, and then in response to light turns on the clock component gene frequency (frq). Froehlich et al. (http://www.sciencemag.org/cgi/content/short/297/5582/815) showed in vitro that WC–1, with its partner WC–2, binds to the regulatory region of frq. Addition of the cofactor flavin adenine dinucleotide (FAD), which binds WC-1, was sufficient to turn the frq on in response to light -- which suggests that WC-1 acts as a blue-light photoreceptor. He et al. (http://www.sciencemag.org/cgi/content/short/297/5582/840) mutated the region of WC–1 that binds FAD, and found that light-induced expression of frq was abolished, providing further support for the light-absorbing role of WC–1. The work demonstrates a simple but unique link between light perception and keeping biological time in Neurospora, as described in an accompanying Perspective by H. Linden (http://www.sciencemag.org/cgi/content/short/297/5582/777).


Genes, Abuse, and Violence

Why do some people who have suffered physical or emotional abuse as children display violent behavior as adults, while others do not? According to a report by Caspi et al. (http://www.sciencemag.org/cgi/content/short/297/5582/851) in the 2 Aug 2002 Science, the answer may lie in a complex interplay of genes and environment. The group found that a certain form of a gene that encodes monoamine oxidase A (MAOA), an enzyme that cleans up excess neurotransmitters in the brain, makes men more likely to be violent -- but only if they were abused as children.

Previous studies have shown that low levels of MAOA activity increase aggressive behavior in both mice and humans. Caspi et al. followed the lives of 442 males (154 of whom were physically or sexually abused as children) living in New Zealand for 26 years beginning from birth. Although only 12% of the men who had been maltreated as children displayed low MAOA activity, they accounted for 44% of the violent crimes committed by the group. On the other hand, children who were mistreated but had higher levels of MAOA were unlikely to develop behavior problems as adults, a finding that suggests that a particular MAOA genotype could protect maltreated children against aggressive behavior. As noted by E. Stokstad in an accompanying news story (http://www.sciencemag.org/cgi/content/short/297/5582/752a), the study shows how a person's genetic make up can influence their sensitivity to social factors and the expression of specific behaviors.


Genomics Reveals Evolutionary Clues

Comparative genomics is blurring the traditional boundaries between two previously separate fields of biology: Evolutionary biologists are now answering fundamental questions using sequence data, while biomedical scientists are using phylogenetic trees to investigate gene function and regulation and human diseases. Two achievements published in Science this month should further bolster this meeting of the minds, and provide valuable insight into evolutionary relationships and the genetic basis for human disease.


Toward Nerve Regeneration

The regrowth of nerve cells after injury to the brain or spinal cord is a holy grail of therapeutic neuroscience. The inability of neurons to regenerate after injury in the mammalian central nervous system (CNS) traces largely to the failure of axons to regrow. That, in turn, can be attributed to two growth-inhibitory proteins -- Nogo and myelin-associated glycoprotein (MAG) -- located within the myelin sheath, a lipid layer that encases CNS axons. While Nogo is known to operate by binding and activating the so-called Nogo receptor, NgR, the receptor for MAG has remained elusive; understanding the mechanisms for both proteins would mark a vital step toward beating the body’s inhibition on axonal growth.

Interestingly, NgR has no transmembrane domain, and therefore must rely on other membrane proteins to mediate its signal and activate intracellular pathways that inhibit nerve regeneration. While attempting to identify these "coreceptors", Liu et al. (http://www.sciencemag.org/cgi/content/short/297/5584/1190) reported an unexpected find in the 16 Aug 2002 Science: that NgR acts as the receptor for both Nogo and MAG. In addition to their expression-cloning studies, the team showed that chemical removal of NgR from chick neuron cell surfaces prevents MAG inhibition of neuronal growth. As noted in an accompanying Perspective by C. J. Woolf and S. Bloechlinger (http://www.sciencemag.org/cgi/content/short/297/5584/1132), the finding that one receptor mediates the activity of both growth inhibitors "opens up exciting possibilities for overcoming axonal growth inhibition, a vital step in neuronal regrowth after brain or spinal cord injury."


Tool-Making Crows

A study by Weir et al. in the Brevia section of the 9 Aug 2002 Science (http://www.sciencemag.org/cgi/content/short/297/5583/981) defied popular conceptions of what it means to have a birdbrain. In the experiments detailed in the study, a captive female New Caledonian crow, confronted with a task that required a curved tool (retrieving a food-containing bucket from a vertical pipe), spontaneously bent a piece of straight wire into a hooked shape, using the newly crafted hook to draw out the food -- and then repeated the behavior in nine out of ten subsequent trials. Though these crows are known to employ tools in the wild using natural materials, this bird had no prior training with the use of pliant materials such as wire. That makes the crow’s apparently instinctive, highly specific problem solving all the more interesting, and raises intriguing questions about the evolutionary preconditions for complex cognition. The crow's behavior was captured on an unusual video clip, available on Science Online (http://www.sciencemag.org/cgi/content/full/297/5583/981/DC1).


Cat and Bird Mating Tales

Two reports in this month's Science explored how social behavior and environmental factors influence animals' reproductive lives:


A Snake and Newt Arms Race

Powerful nations are not the only ones locked in an arms race: every day, predators and prey of all shapes and sizes are striving to out-do one another in the battle for survival. In the 23 Aug 2002 Science, Geffeney et al. (http://www.sciencemag.org/cgi/content/short/297/5585/1336) reported on a fascinating "co-evolutionary arms race" between the garter snake and newts of the genus Taricha. Like the pufferfish and some species of frog and octopus, Taricha newts defend themselves by producing tetrodotoxin, or TTX -- a deadly neurotoxin that paralyzes nerves and muscles by selectively blocking sodium channels. Interestingly, some garter snake populations have evolved resistance to TTX, allowing them to readily feed on newts. But according to the new study, the snakes' clever adaptation comes at a cost: resistant snakes are slower than their more susceptible counterparts. Measurements of muscle action potentials in resistant snakes indicated that TTX-resistant sodium channels are what enable the snakes to evade toxicity. As noted in an accompanying Perspective by R. B. Huey and W. J. Moody (http://www.sciencemag.org/cgi/content/short/297/5585/1289), the results suggest a unique genetic trade-off between resistance and speed, and are likely to "stimulate complementary tests of diverse neurobiological and evolutionary hypotheses."


Progress in Green Chemistry
http://www.sciencemag.org/cgi/content/short/297/5582/798

As the song says, it isn’t easy being green -- but the chemical industry is trying. Decades of reports of air pollution, contaminated groundwater supplies, and other dangerous human health impacts have slowly convinced the industry of the need to pay closer attention to the environmental consequences of chemical production. The 2 Aug 2002 Science dedicated a special section to this increasing movement towards "greening" chemical processes. Three Viewpoint articles detailed recent progress in the field, with a focus on industrial-scale applications. J. M. DeSimone examined practical approaches to reducing use of toxic solvents, including better retaining and recycling procedures and the adoption of solvent-free systems like those employing carbon dioxide. R. A. Gross and B. Kalra described the extraordinary progress in the development and application of biodegradable polymers, including plastics made from starch and cellulose. Despite these advances, implementing change has been challenging and slow. As noted by M. Poliakoff et al., "fundamental changes in technology are adopted by the chemical industry only when they provide a real advantage" -- and it will take collaborative efforts between industry, academia, and government to ensure continued improvement and innovation in green chemistry.


Steering Electrons with Light

How do physical scientists monitor processes that occur in minute fractions of a second? Chemical reactions commonly take place on femtosecond (10^-15) time scales, and scientists have been able to use femtosecond laser pulses to track them. But processes involving electrons -- like ionization -- occur about a thousand times more quickly, and shorter pulses are needed to study them. In the 16 Aug 2002 Science, Kienberger et al. (http://www.sciencemag.org/cgi/content/short/297/5584/1144) described a method to resolve physical processes on the attosecond (10^-18) time scale. The group used high harmonic generation (HHG), in which krypton gas was irradiated with a femtosecond laser pulse, to create attosecond-scale pulses in the soft x-ray range of the electromagnetic spectrum. The krypton sample was then irradiated simultaneously with the x-ray pulse and a laser pulse of visible light, effectively ionizing the krypton atoms. Depending on the timing of the attosecond x-ray pulse and the laser pulse, the researchers were actually able to speed up or slow down the velocity of the electron wavepacket, “steering” it like a classical particle. As discussed in an accompanying Perspective by M. Lewenstein (http://www.sciencemag.org/cgi/content/short/297/5584/1131), the new technique and subsequent refinement of attosecond spectroscopy will likely lead to the development of new diagnostics and, potentially, new ways of controlling molecular and atomic processes.


Vibrationally Excited Water

Water vapor absorbs a significant amount of solar radiation and has profound effects on our atmospheric energy balance and climate -- but how water molecules absorb so much radiation is poorly understood. When wavelengths of light shine through water vapor, they produce characteristic absorption lines in the resulting spectrum. Calculating the theoretical absorption spectrum of water, with which observations can be compared and climate models built, depends in turn on reliable measurements of water's dipole moment, the electrical charge distribution between the oxygen and hydrogen atoms in the molecule. But it has been difficult to get an accurate fix on that quantity using conventional spectroscopy, and thus considerable controversy exists over the accuracy of current water absorption models. A report by Callegari et al. (http://www.sciencemag.org/cgi/content/short/297/5583/993) in the 9 Aug 2002 Science should lend accuracy to the calculations. The team applied an electric field to water vapor molecules, and used laser pulses to excite them. The result: splitting of absorption lines that enabled researchers to precisely measure dipole moments of water vapor in a highly excited state -- the state in which they absorb solar radiation. The new technique should help scientists determine exactly how solar radiation is absorbed in the atmosphere, and help them better understand effects like global warming. A Perspective by P. F. Bernath (http://www.sciencemag.org/cgi/content/short/297/5583/943) accompanied the report.


The Soft Side of Materials Science
http://www.sciencemag.org/cgi/content/short/297/5583/961

Materials scientists are fascinated by why specific materials behave the way they do, what happens when different kinds of materials interact, and how those insights can lead to the creation of new kinds of materials. The 9 Aug 2002 issue of Science explored recent developments in the rapidly expanding area of "soft surface" research, whose relevance ranges from packaging to coatings to biomedicine. A Viewpoint article by T. P. Russell investigated efforts to design polymer-based materials that can respond to a range of external stimuli such as light, pH, and temperature. D. E. Discher and A. Eisenberg explored the world of synthetic polymer vesicles -- microscopic sacs whose encasings mimic the properties of biological membranes. H. Assender et al. reviewed how surface topography -- the “bumpiness” of a material on nanometer scales -- relates to the material's macroscopic properties. And R. R. Matheson Jr. commented on some of the challenges facing the soft-coatings industries, including finding alternatives to toxic chemicals, designing coatings resistant to specific biological factors, and improving the strength and longevity of existing coatings. Meanwhile, a news article by R. F. Service examined biosensor technology -- efforts to fashion small devices that can be implanted in the body to help track early signs of disease or monitor glucose levels -- for which the major factor impeding progress is the immune system's mission to attack everything "foreign."


Earth Shifts Its Weight

As most of us learned in school, Earth is not a perfect sphere, but an "oblate spheroid" -- narrower at the poles and wider at the equator, owing to the planet's axial spin. Satellite laser-ranging data from the last 20 years indicates that Earth has actually become slightly more spherical over time, as the polar regions, weighed down by an enormous ice sheet during the last ice age, have gradually rebounded since the ice retreated. But a report by Cox and Chao (http://www.sciencemag.org/cgi/content/short/297/5582/831) in the 2 Aug 2002 Science suggested that the trend reversed abruptly about four years ago -- and that Earth is now again getting fatter around the middle. The team combined data from nine satellite records to develop an estimate of changes over time in “J2,” the component of Earth’s gravity field that measures the planet’s oblateness, and found that J2 increased sharply beginning in 1998 -- implying that Earth’s circumference at the equator has expanded by close to a millimeter since then. The data indicate a large-scale mass transfer from high to low latitudes. The redistribution of mass could stem from changes in ocean circulation or from sudden mass redistribution in Earth’s fluid outer core. As noted in an accompanying Perspective by A. Cazenave and R. S. Nerem (http://www.sciencemag.org/cgi/content/short/297/5582/783), two new technologies -- state-of-the-art ocean general circulation models, and the recently launched satellite mission GRACE (Gravity Recovery and Climate Experiment) -- may provide some clues on how and why Earth’s weight is shifting.


A Warm Polar Outlook
http://www.sciencemag.org/cgi/content/short/297/5586/1489

Melting ice sheets, rising sea levels, and increased concentration of greenhouse gases all point to an undeniable trend: our world is warming. A special issue of Science on 30 Aug 2002 examined how the planet's polar regions have changed in response to global climate change in recent decades, and what the future holds for these frigid expanses. A review article by R. E. Moritz et al. discussed the dynamics of recent climate change in the Arctic, and emphasized that reliable projection of future climate change will require reconciliation of climate model predictions with real data on the effects of human- induced warming. E. Rignot and R. H. Thomas reviewed our current understanding of the mass balance of polar ice sheets in Greenland and Antarctica, an understanding that has been greatly enhanced by remote-sensing technologies. Meanwhile, F. Dominé and P. B. Shepson discussed air-snow interactions and their effect on atmospheric chemistry. J.P. Croxall et al. examined the influence sea- ice changes are having on three species of Antarctic seabirds, and could have on future food chain dynamics.

Finally, three news articles hinted at a perilous future if current polar trends continue. R. A. Kerr described how a predicted "ice-less" Northwest Passage in the Arctic Ocean will impact nautical traffic through the region and thus indigenous human and animal populations. E. Goldman described the dangers posed by melting permafrost. And J. Kaiser explained how eroding ice shelves on the Antarctic Peninsula are providing a threatening snapshot of what might happen if global warming causes mainland ice sheets to melt.


A final word from our sponsor:

ZOOM® INTO FAST AND ACCURATE RESULTS

When you're racing to be first, you need rapid, accurate analysis methods. Use the ZOOM® IPGRunner™ system for your 2D electrophoresis studies and achieve reliable results faster than with traditional procedures.

For more information, visit http://www.invitrogen.com/ZOOM today.

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